Background filters are affected by masks

cc/output/shader.h

Index: cc/output/shader.h
diff --git a/cc/output/shader.h b/cc/output/shader.h
index 7ef6ea9a7dfb4b9e9d8baa98071090cb156ba7c0..cc83700b83896f9fd800a89713583eb38571f66e 100644
--- a/cc/output/shader.h
+++ b/cc/output/shader.h
@@ -76,6 +76,7 @@ struct ShaderLocations {
   int tex_transform = -1;
   int backdrop = -1;
   int backdrop_rect = -1;
+  int original_backdrop = -1;
 };
 
 // Note: The highp_threshold_cache must be provided by the caller to make
@@ -346,11 +347,16 @@ class VertexShaderVideoTransform {
 class FragmentTexBlendMode {
  public:
   int backdrop_location() const { return backdrop_location_; }
+  int original_backdrop_location() const { return original_backdrop_location_; }
   int backdrop_rect_location() const { return backdrop_rect_location_; }
 
   BlendMode blend_mode() const { return blend_mode_; }
   void set_blend_mode(BlendMode blend_mode) { blend_mode_ = blend_mode; }
   bool has_blend_mode() const { return blend_mode_ != BLEND_MODE_NONE; }
+  void set_mask_for_background(bool mask_for_background) {
+    mask_for_background_ = mask_for_background;
+  }
+  bool mask_for_background() const { return mask_for_background_; }
 
  protected:
   FragmentTexBlendMode();
@@ -358,10 +364,12 @@ class FragmentTexBlendMode {
   std::string SetBlendModeFunctions(std::string shader_string) const;
 
   int backdrop_location_;
+  int original_backdrop_location_;
   int backdrop_rect_location_;
 
  private:
   BlendMode blend_mode_;
+  bool mask_for_background_;
 
   std::string GetHelperFunctions() const;
   std::string GetBlendFunction() const;
@@ -597,7 +605,7 @@ class FragmentShaderRGBATexAlphaMask : public FragmentTexBlendMode {
   std::string GetShaderString(
       TexCoordPrecision precision, SamplerType sampler) const;
   static std::string GetShaderHead();
-  static std::string GetShaderBody();
+  static std::string GetShaderBody(bool mask_for_background);
   void FillLocations(ShaderLocations* locations) const;
   void Init(gpu::gles2::GLES2Interface* context,
             unsigned program,
@@ -628,7 +636,7 @@ class FragmentShaderRGBATexAlphaMaskAA : public FragmentTexBlendMode {
   std::string GetShaderString(
       TexCoordPrecision precision, SamplerType sampler) const;
   static std::string GetShaderHead();
-  static std::string GetShaderBody();
+  static std::string GetShaderBody(bool mask_for_background);
   void FillLocations(ShaderLocations* locations) const;
   void Init(gpu::gles2::GLES2Interface* context,
             unsigned program,
@@ -660,7 +668,7 @@ class FragmentShaderRGBATexAlphaMaskColorMatrixAA
   std::string GetShaderString(
       TexCoordPrecision precision, SamplerType sampler) const;
   static std::string GetShaderHead();
-  static std::string GetShaderBody();
+  static std::string GetShaderBody(bool mask_for_background);
   void FillLocations(ShaderLocations* locations) const;
   void Init(gpu::gles2::GLES2Interface* context,
             unsigned program,
@@ -716,7 +724,7 @@ class FragmentShaderRGBATexAlphaMaskColorMatrix : public FragmentTexBlendMode {
   std::string GetShaderString(
       TexCoordPrecision precision, SamplerType sampler) const;
   static std::string GetShaderHead();
-  static std::string GetShaderBody();
+  static std::string GetShaderBody(bool mask_for_background);
   void FillLocations(ShaderLocations* locations) const;
   void Init(gpu::gles2::GLES2Interface* context,
             unsigned program,