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 e7273a8c12cd1bddee6756b6ade8434564aa8cd5..f4093016c27469b100d4f3ac14c9867ca2762a69 100644
--- a/cc/output/software_renderer.cc
+++ b/cc/output/software_renderer.cc
@@ -352,11 +352,31 @@ 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 = (SkColorGetA(quad->background_color) != 0) &&
+                          !bitmap->isOpaque(); 
+  bool needs_layer = blend_background && (current_paint_.getAlpha() != 0xFF);

[alokp, 2013/07/09 00:08:06]

reed@: Is there a paint mode in skia that will avoid having to create this
offscreen buffer?

We need to blend a bitmap over a solid color; blend the result with a global
alpha.

+  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,