Make WebMouseEvent.windowX equal to WebMouseEvent.x. Same for y.
Make WebMouseEvent.windowX equal to WebMouseEvent.x. Same for y.

The (windowX,windowY) coordinates affected by this CL are not
used anywhere: the modified WebMouseEvents ultimately reach
PepperPluginInstanceImpl::HandleInputEvent() which never uses the
(windowX,windowY) coordinate.

This is on our way to nuke the redundant WebMouseEvent.windowX and
.windowY fields. Almost all other assignments to (windowX,windowY)
are equal to (x,y), so we are normalizing the use cases before nuking.

BUG=507787

Review URL: https://codereview.chromium.org/1227823006

Cr-Commit-Position: 972c6d2dc6dd5efdad1377c0d224e03eb8f276f7@{#338342}

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