Blend TextureLayer background-color at draw time.

cc/output/software_renderer.cc

Index: cc/output/software_renderer.cc
diff --git a/cc/output/software_renderer.cc b/cc/output/software_renderer.cc
index 817bb679be7538759ed3e46c221130fc316ed132..5c745c0e0dba0bf2baa5ca51f275cb74befd738f 100644
--- a/cc/output/software_renderer.cc
+++ b/cc/output/software_renderer.cc
@@ -353,11 +353,31 @@ void SoftwareRenderer::DrawTextureQuad(const DrawingFrame* frame,
                                       bitmap->width(),
                                       bitmap->height());
   SkRect sk_uv_rect = gfx::RectFToSkRect(uv_rect);
+  SkRect quad_rect = gfx::RectFToSkRect(QuadVertexRect());
+
   if (quad->flipped)
     current_canvas_->scale(1, -1);
-  current_canvas_->drawBitmapRectToRect(*bitmap, &sk_uv_rect,
-                                        gfx::RectFToSkRect(QuadVertexRect()),
+
+  bool blend_background = quad->background_color != SK_ColorTRANSPARENT &&
+                          !bitmap->isOpaque();
+  bool needs_layer = blend_background && (current_paint_.getAlpha() != 0xFF);
+  if (needs_layer) {
+    current_canvas_->saveLayerAlpha(&quad_rect, current_paint_.getAlpha());
+    current_paint_.setAlpha(0xFF);
+  }
+  if (blend_background) {
+    SkPaint background_paint;
+    background_paint.setColor(quad->background_color);
+    current_canvas_->drawRect(quad_rect, background_paint);
+  }
+
+  current_canvas_->drawBitmapRectToRect(*bitmap,
+                                        &sk_uv_rect,
+                                        quad_rect,
                                         &current_paint_);
+
+  if (needs_layer)
+    current_canvas_->restore();
 }
 
 void SoftwareRenderer::DrawTileQuad(const DrawingFrame* frame,