Chromium compositor change implementing page-scale driven pinch-zoom.

content/renderer/render_view_impl.cc

Index: content/renderer/render_view_impl.cc
===================================================================
--- content/renderer/render_view_impl.cc	(revision 160227)
+++ content/renderer/render_view_impl.cc	(working copy)
@@ -3151,6 +3151,8 @@
       command_line.HasSwitch(switches::kEnableFixedLayout);
   bool enable_pinch = enable_viewport ||
                       command_line.HasSwitch(switches::kEnablePinch);
+  bool enable_pinch_in_compositor =
+      command_line.HasSwitch(switches::kEnablePinchInCompositor);
 
   webview()->enableFixedLayoutMode(enable_fixed_layout || enable_viewport);
   webview()->settings()->setFixedElementsLayoutRelativeToFrame(true);
@@ -3163,6 +3165,10 @@
     webview()->setPageScaleFactorLimits(1, 1);
   }
 
+  if (enable_pinch_in_compositor &&
+      webview()->isAcceleratedCompositingActive())
+    webview()->setPageScaleFactorLimits(1, 4);

[piman, 2012/10/05 00:01:08]

note: this is possibly racy. isAcceleratedCompositingActive() may not be true
now, but could change later. Should we do this as well on
didActivateCompositor()?

[Jeff Timanus, 2012/10/05 00:05:34]

If this is racey, are the other conditions also racey?  They are also gated on
isAccelratedCompositingActive().

[piman, 2012/10/05 00:25:51]

Most likely, yes.

[Jeff Timanus, 2012/10/05 15:37:50]

I'm not sure if fixing these races is appropriate for this change.  I've already
touched a lot of files here.  I think filing a bug and a follow-up change would
be better.  Agree?

+
   if (enable_viewport) {
     webview()->settings()->setViewportEnabled(true);
   } else if (enable_fixed_layout) {