Allow using a larger-than-necessary texture as cached render pass backing

cc/render_surface_impl.cc

Index: cc/render_surface_impl.cc
diff --git a/cc/render_surface_impl.cc b/cc/render_surface_impl.cc
index 800faedd8a54e7f2d9375f318202f5b3bc2e5b32..6ba520226aed80188cd88df1f5410ae5d4a99d39 100644
--- a/cc/render_surface_impl.cc
+++ b/cc/render_surface_impl.cc
@@ -225,15 +225,12 @@ void RenderSurfaceImpl::appendQuads(QuadSink& quadSink, AppendQuadsData& appendQ
             maskLayer = 0;
     }
 
-    float maskTexCoordScaleX = 1;
-    float maskTexCoordScaleY = 1;
-    float maskTexCoordOffsetX = 0;
-    float maskTexCoordOffsetY = 0;
+    gfx::RectF mask_uv_rect(0.0f, 0.0f, 1.0f, 1.0f);
     if (maskLayer) {
-        maskTexCoordScaleX = contentRect().width() / maskLayer->contentsScaleX() / maskLayer->bounds().width();
-        maskTexCoordScaleY = contentRect().height() / maskLayer->contentsScaleY() / maskLayer->bounds().height();
-        maskTexCoordOffsetX = static_cast<float>(contentRect().x()) / contentRect().width() * maskTexCoordScaleX;
-        maskTexCoordOffsetY = static_cast<float>(contentRect().y()) / contentRect().height() * maskTexCoordScaleY;
+        mask_uv_rect.set_width(contentRect().width() / maskLayer->contentsScaleX() / maskLayer->bounds().width());
+        mask_uv_rect.set_height(contentRect().height() / maskLayer->contentsScaleY() / maskLayer->bounds().height());
+        mask_uv_rect.set_x(static_cast<float>(contentRect().x()) / contentRect().width() * mask_uv_rect.width());
+        mask_uv_rect.set_y(static_cast<float>(contentRect().y()) / contentRect().height() * mask_uv_rect.height());
     }
 
     ResourceProvider::ResourceId maskResourceId = maskLayer ? maskLayer->contentsResourceId() : 0;
@@ -241,7 +238,7 @@ void RenderSurfaceImpl::appendQuads(QuadSink& quadSink, AppendQuadsData& appendQ
 
     scoped_ptr<RenderPassDrawQuad> quad = RenderPassDrawQuad::Create();
     quad->SetNew(sharedQuadState, contentRect(), renderPassId, forReplica, maskResourceId, contentsChangedSinceLastFrame,
-                 maskTexCoordScaleX, maskTexCoordScaleY, maskTexCoordOffsetX, maskTexCoordOffsetY);
+                 mask_uv_rect);
     quadSink.append(quad.PassAs<DrawQuad>(), appendQuadsData);
 }