Tiling priorities in Android Webview.

android_webview/browser/browser_view_renderer.cc

Index: android_webview/browser/browser_view_renderer.cc
diff --git a/android_webview/browser/browser_view_renderer.cc b/android_webview/browser/browser_view_renderer.cc
index fd00b6be6b701a1c054c305d7ccadf9ae3f1890b..77bd2f9948e4cee4ee26811c6011b108df1974b6 100644
--- a/android_webview/browser/browser_view_renderer.cc
+++ b/android_webview/browser/browser_view_renderer.cc
@@ -5,6 +5,7 @@
 #include "android_webview/browser/browser_view_renderer.h"
 
 #include "android_webview/browser/browser_view_renderer_client.h"
+#include "android_webview/browser/parent_compositor_draw_constraints.h"
 #include "android_webview/browser/shared_renderer_state.h"
 #include "android_webview/common/aw_switches.h"
 #include "android_webview/public/browser/draw_gl.h"
@@ -258,14 +259,29 @@ bool BrowserViewRenderer::OnDrawHardware(jobject java_canvas) {
   draw_gl_input->width = width_;
   draw_gl_input->height = height_;
 
-  gfx::Transform transform;
   gfx::Size surface_size(width_, height_);
   gfx::Rect viewport(surface_size);
-  // TODO(boliu): Should really be |last_on_draw_global_visible_rect_|.
-  // See crbug.com/372073.
   gfx::Rect clip = viewport;
-  scoped_ptr<cc::CompositorFrame> frame = compositor_->DemandDrawHw(
-      surface_size, transform, viewport, clip);
+  gfx::Rect external_tiling_rect;
+  gfx::Transform external_tiling_transform = parent_draw_constraints_.transform;
+
+  parent_draw_constraints_ = shared_renderer_state_->ParentDrawConstraints();
+
+  // If the WebView is on a layer, the parent transform is just an identity
+  // matrix and WebView does not know what transform is applied onto the layer.
+  // In this case, just use the surface rect for tiling.
+  if (parent_draw_constraints_.is_layer)
+    external_tiling_rect = parent_draw_constraints_.surface_rect;
+  else
+    external_tiling_rect = last_on_draw_global_visible_rect_;
+
+  scoped_ptr<cc::CompositorFrame> frame =
+      compositor_->DemandDrawHw(surface_size,
+                                gfx::Transform(),
+                                viewport,
+                                clip,
+                                external_tiling_rect,
+                                external_tiling_transform);
   if (!frame.get())
     return false;