|handling_key_event_| flag should be set correctly.
|handling_key_event_| flag should be set correctly.

Fixed the issue that the |handling_key_event_| flag is wrongly set so
that SetComposition (from virtual keyboard) without a physical key event
doesn't work.

TBR=nona@chromium.org
BUG=498633
TEST=Verified on sandbox.

Review URL: https://codereview.chromium.org/1176313002

Cr-Commit-Position: 972c6d2dc6dd5efdad1377c0d224e03eb8f276f7@{#333906}

Just-D/chromium-1,hgl888/chromium-crosswalk,Pluto-tv/chromium-crosswalk,TheTypoMaster/chromium-crosswalk,Pluto-tv/chromium-crosswalk,chuan9/chromium-crosswalk,axinging/chromium-crosswalk,Pluto-tv/chromium-crosswalk,chuan9/chromium-crosswalk,axinging/chromium-crosswalk,Pluto-tv/chromium-crosswalk,hgl888/chromium-crosswalk,axinging/chromium-crosswalk,chuan9/chromium-crosswalk,axinging/chromium-crosswalk,Just-D/chromium-1,TheTypoMaster/chromium-crosswalk,chuan9/chromium-crosswalk,Just-D/chromium-1,chuan9/chromium-crosswalk,Pluto-tv/chromium-crosswalk,TheTypoMaster/chromium-crosswalk,axinging/chromium-crosswalk,Chilledheart/chromium,chuan9/chromium-crosswalk,TheTypoMaster/chromium-crosswalk,TheTypoMaster/chromium-crosswalk,Chilledheart/chromium,Just-D/chromium-1,TheTypoMaster/chromium-crosswalk,axinging/chromium-crosswalk,Just-D/chromium-1,Chilledheart/chromium,axinging/chromium-crosswalk,Chilledheart/chromium,axinging/chromium-crosswalk,chuan9/chromium-crosswalk,TheTypoMaster/chromium-crosswalk,axinging/chromium-crosswalk,Pluto-tv/chromium-crosswalk,Chilledheart/chromium,Chilledheart/chromium,TheTypoMaster/chromium-crosswalk,Just-D/chromium-1,hgl888/chromium-crosswalk,TheTypoMaster/chromium-crosswalk,Pluto-tv/chromium-crosswalk,Just-D/chromium-1,Chilledheart/chromium,axinging/chromium-crosswalk,chuan9/chromium-crosswalk,hgl888/chromium-crosswalk,hgl888/chromium-crosswalk,hgl888/chromium-crosswalk,Pluto-tv/chromium-crosswalk,Chilledheart/chromium,Just-D/chromium-1,chuan9/chromium-crosswalk,Just-D/chromium-1,axinging/chromium-crosswalk,Chilledheart/chromium,hgl888/chromium-crosswalk,hgl888/chromium-crosswalk,hgl888/chromium-crosswalk,Pluto-tv/chromium-crosswalk