Implement hidpi and pinch-zoom scaling of filter params in cc.

cc/output/gl_renderer.cc

Index: cc/output/gl_renderer.cc
diff --git a/cc/output/gl_renderer.cc b/cc/output/gl_renderer.cc
index a262e370a204685bf660c9c3110c912890882a14..db39d5ccfcfe3708355ba298bfd9abd592839f51 100644
--- a/cc/output/gl_renderer.cc
+++ b/cc/output/gl_renderer.cc
@@ -484,6 +484,7 @@ void GLRenderer::DrawDebugBorderQuad(const DrawingFrame* frame,
 static SkBitmap ApplyImageFilter(GLRenderer* renderer,
                                  ContextProvider* offscreen_contexts,
                                  const gfx::Point& origin,
+                                 const gfx::Transform& scale,
                                  SkImageFilter* filter,
                                  ScopedResource* source_texture_resource) {
   if (!filter)
@@ -547,10 +548,8 @@ static SkBitmap ApplyImageFilter(GLRenderer* renderer,
   paint.setImageFilter(filter);
   canvas.clear(SK_ColorTRANSPARENT);
 
-  // TODO(senorblanco): in addition to the origin translation here, the canvas
-  // should also be scaled to accomodate device pixel ratio and pinch zoom. See
-  // crbug.com/281516 and crbug.com/281518.
   canvas.translate(SkIntToScalar(-origin.x()), SkIntToScalar(-origin.y()));
+  canvas.scale(scale.Scale2d().x(), scale.Scale2d().y());

[danakj, 2014/03/07 17:35:44]

Huh, didn't know we have Scale2d(). MathUtil::ComputeTransform2dScaleComponents
is more rigorous, but I'm not sure if it would matter here or not.

   canvas.drawSprite(source, 0, 0, &paint);
 
   // Flush skia context so that all the rendered stuff appears on the
@@ -762,6 +761,7 @@ scoped_ptr<ScopedResource> GLRenderer::GetBackgroundWithFilters(
         ApplyImageFilter(this,
                          frame->offscreen_context_provider,
                          quad->rect.origin(),
+                         quad->scale,
                          filter.get(),
                          device_background_texture.get());
   }
@@ -896,6 +896,7 @@ void GLRenderer::DrawRenderPassQuad(DrawingFrame* frame,
         filter_bitmap = ApplyImageFilter(this,
                                          frame->offscreen_context_provider,
                                          quad->rect.origin(),
+                                         quad->scale,
                                          filter.get(),
                                          contents_texture);
       }