Implement transform/clip support for Android WebView.

cc/output/output_surface.cc

Index: cc/output/output_surface.cc
diff --git a/cc/output/output_surface.cc b/cc/output/output_surface.cc
index fe2b074ee46d033f7900054ccb164dc3b3992cae..051b5fc92397887debdf23b6d0def74afde7cab1 100644
--- a/cc/output/output_surface.cc
+++ b/cc/output/output_surface.cc
@@ -112,8 +112,18 @@ void OutputSurface::DiscardBackbuffer() {
 }
 
 void OutputSurface::Reshape(gfx::Size size, float scale_factor) {
-  DCHECK(context3d_);
-  context3d_->reshapeWithScaleFactor(size.width(), size.height(), scale_factor);
+  if (size == surface_size_ && scale_factor == device_scale_factor_)
+    return;
+
+  surface_size_ = size;
+  device_scale_factor_ = scale_factor;
+  if (context3d_)
+    context3d_->reshapeWithScaleFactor(
+        size.width(), size.height(), scale_factor);
+}
+
+gfx::Size OutputSurface::SurfaceSize() const {
+  return surface_size_;
 }
 
 void OutputSurface::BindFramebuffer() {