Fix up-scaling case to early-exit if no updates are within clip area.
Fix up-scaling case to early-exit if no updates are within clip area.

The RectangleUpdateDecoder expects Decoders to report an empty update region if no updates lay within the clip area, to provide rendering flow-control. The VP8 Decoder was always reporting the entire frame as having been rendered when up-scaling, resulting in continuous re-rendering of the frame.

BUG=116835,133609
TEST=Run Chromoting client with page-zoom >100% to a host with little or no changes happening on-screen and verify that the client's CPU usage is not >50%.

Review URL: https://chromiumcodereview.appspot.com/10576017

git-svn-id: de016e52bd170d2d4f2344f9bf92d50478b649e0@143132 0039d316-1c4b-4281-b951-d872f2087c98

hujiajie/pa-chromium,krieger-od/nwjs_chromium.src,mogoweb/chromium-crosswalk,axinging/chromium-crosswalk,zcbenz/cefode-chromium,timopulkkinen/BubbleFish,TheTypoMaster/chromium-crosswalk,nacl-webkit/chrome_deps,TheTypoMaster/chromium-crosswalk,nacl-webkit/chrome_deps,fujunwei/chromium-crosswalk,Just-D/chromium-1,Jonekee/chromium.src,zcbenz/cefode-chromium,junmin-zhu/chromium-rivertrail,pozdnyakov/chromium-crosswalk,fujunwei/chromium-crosswalk,axinging/chromium-crosswalk,zcbenz/cefode-chromium,Just-D/chromium-1,timopulkkinen/BubbleFish,hgl888/chromium-crosswalk-efl,ChromiumWebApps/chromium,bright-sparks/chromium-spacewalk,timopulkkinen/BubbleFish,patrickm/chromium.src,nacl-webkit/chrome_deps,jaruba/chromium.src,dushu1203/chromium.src,dushu1203/chromium.src,hujiajie/pa-chromium,junmin-zhu/chromium-rivertrail,littlstar/chromium.src,anirudhSK/chromium,hgl888/chromium-crosswalk-efl,ltilve/chromium,ondra-novak/chromium.src,dushu1203/chromium.src,M4sse/chromium.src,ChromiumWebApps/chromium,chuan9/chromium-crosswalk,hgl888/chromium-crosswalk-efl,ltilve/chromium,dednal/chromium.src,keishi/chromium,ChromiumWebApps/chromium,PeterWangIntel/chromium-crosswalk,krieger-od/nwjs_chromium.src,junmin-zhu/chromium-rivertrail,Jonekee/chromium.src,crosswalk-project/chromium-crosswalk-efl,jaruba/chromium.src,hujiajie/pa-chromium,nacl-webkit/chrome_deps,Just-D/chromium-1,hgl888/chromium-crosswalk-efl,keishi/chromium,Jonekee/chromium.src,ltilve/chromium,ChromiumWebApps/chromium,Fireblend/chromium-crosswalk,pozdnyakov/chromium-crosswalk,markYoungH/chromium.src,hgl888/chromium-crosswalk,junmin-zhu/chromium-rivertrail,hgl888/chromium-crosswalk,mogoweb/chromium-crosswalk,Fireblend/chromium-crosswalk,chuan9/chromium-crosswalk,markYoungH/chromium.src,hujiajie/pa-chromium,TheTypoMaster/chromium-crosswalk,jaruba/chromium.src,krieger-od/nwjs_chromium.src,markYoungH/chromium.src,M4sse/chromium.src,hujiajie/pa-chromium,zcbenz/cefode-chromium,markYoungH/chromium.src,Jonekee/chromium.src,markYoungH/chromium.src,chuan9/chromium-crosswalk,Jonekee/chromium.src,markYoungH/chromium.src,chuan9/chromium-crosswalk,Fireblend/chromium-crosswalk,Fireblend/chromium-crosswalk,mohamed--abdel-maksoud/chromium.src,ondra-novak/chromium.src,nacl-webkit/chrome_deps,TheTypoMaster/chromium-crosswalk,mogoweb/chromium-crosswalk,dushu1203/chromium.src,PeterWangIntel/chromium-crosswalk,krieger-od/nwjs_chromium.src,Pluto-tv/chromium-crosswalk,anirudhSK/chromium,axinging/chromium-crosswalk,fujunwei/chromium-crosswalk,crosswalk-project/chromium-crosswalk-efl,TheTypoMaster/chromium-crosswalk,krieger-od/nwjs_chromium.src,anirudhSK/chromium,mogoweb/chromium-crosswalk,TheTypoMaster/chromium-crosswalk,PeterWangIntel/chromium-crosswalk,nacl-webkit/chrome_deps,zcbenz/cefode-chromium,axinging/chromium-crosswalk,ChromiumWebApps/chromium,hgl888/chromium-crosswalk-efl,littlstar/chromium.src,hujiajie/pa-chromium,PeterWangIntel/chromium-crosswalk,junmin-zhu/chromium-rivertrail,hgl888/chromium-crosswalk-efl,littlstar/chromium.src,axinging/chromium-crosswalk,Pluto-tv/chromium-crosswalk,mohamed--abdel-maksoud/chromium.src,TheTypoMaster/chromium-crosswalk,nacl-webkit/chrome_deps,krieger-od/nwjs_chromium.src,hujiajie/pa-chromium,littlstar/chromium.src,anirudhSK/chromium,M4sse/chromium.src,fujunwei/chromium-crosswalk,fujunwei/chromium-crosswalk,dednal/chromium.src,TheTypoMaster/chromium-crosswalk,mohamed--abdel-maksoud/chromium.src,ltilve/chromium,Pluto-tv/chromium-crosswalk,dednal/chromium.src,crosswalk-project/chromium-crosswalk-efl,Pluto-tv/chromium-crosswalk,dednal/chromium.src,dushu1203/chromium.src,anirudhSK/chromium,jaruba/chromium.src,Chilledheart/chromium,krieger-od/nwjs_chromium.src,PeterWangIntel/chromium-crosswalk,Just-D/chromium-1,zcbenz/cefode-chromium,jaruba/chromium.src,hujiajie/pa-chromium,Just-D/chromium-1,ltilve/chromium,Just-D/chromium-1,fujunwei/chromium-crosswalk,dushu1203/chromium.src,ondra-novak/chromium.src,pozdnyakov/chromium-crosswalk,Just-D/chromium-1,Fireblend/chromium-crosswalk,timopulkkinen/BubbleFish,Fireblend/chromium-crosswalk,Chilledheart/chromium,littlstar/chromium.src,ondra-novak/chromium.src,Jonekee/chromium.src,M4sse/chromium.src,timopulkkinen/BubbleFish,axinging/chromium-crosswalk,dushu1203/chromium.src,littlstar/chromium.src,bright-sparks/chromium-spacewalk,hgl888/chromium-crosswalk-efl,anirudhSK/chromium,bright-sparks/chromium-spacewalk,crosswalk-project/chromium-crosswalk-efl,axinging/chromium-crosswalk,dushu1203/chromium.src,axinging/chromium-crosswalk,Chilledheart/chromium,pozdnyakov/chromium-crosswalk,dushu1203/chromium.src,patrickm/chromium.src,crosswalk-project/chromium-crosswalk-efl,hgl888/chromium-crosswalk,mohamed--abdel-maksoud/chromium.src,junmin-zhu/chromium-rivertrail,krieger-od/nwjs_chromium.src,Pluto-tv/chromium-crosswalk,keishi/chromium,timopulkkinen/BubbleFish,pozdnyakov/chromium-crosswalk,Just-D/chromium-1,ltilve/chromium,crosswalk-project/chromium-crosswalk-efl,hgl888/chromium-crosswalk-efl,PeterWangIntel/chromium-crosswalk,junmin-zhu/chromium-rivertrail,anirudhSK/chromium,hgl888/chromium-crosswalk,hujiajie/pa-chromium,axinging/chromium-crosswalk,jaruba/chromium.src,anirudhSK/chromium,patrickm/chromium.src,timopulkkinen/BubbleFish,anirudhSK/chromium,mohamed--abdel-maksoud/chromium.src,bright-sparks/chromium-spacewalk,dednal/chromium.src,ChromiumWebApps/chromium,patrickm/chromium.src,jaruba/chromium.src,Fireblend/chromium-crosswalk,jaruba/chromium.src,keishi/chromium,nacl-webkit/chrome_deps,zcbenz/cefode-chromium,fujunwei/chromium-crosswalk,ChromiumWebApps/chromium,dednal/chromium.src,zcbenz/cefode-chromium,Pluto-tv/chromium-crosswalk,junmin-zhu/chromium-rivertrail,Jonekee/chromium.src,M4sse/chromium.src,dednal/chromium.src,Pluto-tv/chromium-crosswalk,Chilledheart/chromium,chuan9/chromium-crosswalk,jaruba/chromium.src,mohamed--abdel-maksoud/chromium.src,markYoungH/chromium.src,dednal/chromium.src,keishi/chromium,jaruba/chromium.src,dednal/chromium.src,axinging/chromium-crosswalk,bright-sparks/chromium-spacewalk,hujiajie/pa-chromium,M4sse/chromium.src,Jonekee/chromium.src,markYoungH/chromium.src,zcbenz/cefode-chromium,krieger-od/nwjs_chromium.src,mogoweb/chromium-crosswalk,bright-sparks/chromium-spacewalk,dednal/chromium.src,hgl888/chromium-crosswalk,Fireblend/chromium-crosswalk,krieger-od/nwjs_chromium.src,Chilledheart/chromium,anirudhSK/chromium,bright-sparks/chromium-spacewalk,anirudhSK/chromium,ondra-novak/chromium.src,mohamed--abdel-maksoud/chromium.src,zcbenz/cefode-chromium,chuan9/chromium-crosswalk,ChromiumWebApps/chromium,timopulkkinen/BubbleFish,Pluto-tv/chromium-crosswalk,keishi/chromium,junmin-zhu/chromium-rivertrail,PeterWangIntel/chromium-crosswalk,crosswalk-project/chromium-crosswalk-efl,Just-D/chromium-1,pozdnyakov/chromium-crosswalk,markYoungH/chromium.src,ondra-novak/chromium.src,dushu1203/chromium.src,ondra-novak/chromium.src,Chilledheart/chromium,mogoweb/chromium-crosswalk,chuan9/chromium-crosswalk,pozdnyakov/chromium-crosswalk,PeterWangIntel/chromium-crosswalk,mohamed--abdel-maksoud/chromium.src,nacl-webkit/chrome_deps,hgl888/chromium-crosswalk,pozdnyakov/chromium-crosswalk,patrickm/chromium.src,littlstar/chromium.src,ondra-novak/chromium.src,ondra-novak/chromium.src,mogoweb/chromium-crosswalk,patrickm/chromium.src,dednal/chromium.src,timopulkkinen/BubbleFish,ltilve/chromium,ltilve/chromium,keishi/chromium,hgl888/chromium-crosswalk-efl,M4sse/chromium.src,fujunwei/chromium-crosswalk,mogoweb/chromium-crosswalk,ChromiumWebApps/chromium,M4sse/chromium.src,hujiajie/pa-chromium,PeterWangIntel/chromium-crosswalk,hgl888/chromium-crosswalk,chuan9/chromium-crosswalk,keishi/chromium,pozdnyakov/chromium-crosswalk,jaruba/chromium.src,M4sse/chromium.src,keishi/chromium,ChromiumWebApps/chromium,pozdnyakov/chromium-crosswalk,M4sse/chromium.src,Chilledheart/chromium,hgl888/chromium-crosswalk,hgl888/chromium-crosswalk-efl,Pluto-tv/chromium-crosswalk,ltilve/chromium,ChromiumWebApps/chromium,Chilledheart/chromium,bright-sparks/chromium-spacewalk,zcbenz/cefode-chromium,timopulkkinen/BubbleFish,axinging/chromium-crosswalk,anirudhSK/chromium,junmin-zhu/chromium-rivertrail,keishi/chromium,nacl-webkit/chrome_deps,M4sse/chromium.src,mohamed--abdel-maksoud/chromium.src,chuan9/chromium-crosswalk,patrickm/chromium.src,pozdnyakov/chromium-crosswalk,ChromiumWebApps/chromium,Fireblend/chromium-crosswalk,hgl888/chromium-crosswalk,mohamed--abdel-maksoud/chromium.src,markYoungH/chromium.src,Jonekee/chromium.src,krieger-od/nwjs_chromium.src,bright-sparks/chromium-spacewalk,markYoungH/chromium.src,littlstar/chromium.src,fujunwei/chromium-crosswalk,junmin-zhu/chromium-rivertrail,crosswalk-project/chromium-crosswalk-efl,nacl-webkit/chrome_deps,mogoweb/chromium-crosswalk,Jonekee/chromium.src,dushu1203/chromium.src,crosswalk-project/chromium-crosswalk-efl,patrickm/chromium.src,mogoweb/chromium-crosswalk,keishi/chromium,mohamed--abdel-maksoud/chromium.src,patrickm/chromium.src,Chilledheart/chromium,timopulkkinen/BubbleFish,Jonekee/chromium.src,TheTypoMaster/chromium-crosswalk