Blend TextureLayer background-color at draw time.

cc/output/shader.cc

Index: cc/output/shader.cc
diff --git a/cc/output/shader.cc b/cc/output/shader.cc
index 6e1f6c5a915f341354100f7ea92021ef81bfde48..ef88ff586d190106e1eced76492d843827119bcc 100644
--- a/cc/output/shader.cc
+++ b/cc/output/shader.cc
@@ -668,30 +668,65 @@ std::string FragmentShaderRGBATexColorMatrixAlpha::GetShaderString(
   );  // NOLINT(whitespace/parens)
 }
 
-std::string FragmentShaderRGBATexVaryingAlpha::GetShaderString(
+FragmentTexBackgroundBinding::FragmentTexBackgroundBinding()
+    : background_color_location_(-1),
+      sampler_location_(-1) {
+}
+
+void FragmentTexBackgroundBinding::Init(WebGraphicsContext3D* context,
+                                        unsigned program,
+                                        bool using_bind_uniform,
+                                        int* base_uniform_index) {
+  static const char* shader_uniforms[] = {
+    "s_texture",
+    "background_color",
+  };
+  int locations[2];
+
+  GetProgramUniformLocations(context,
+                             program,
+                             shader_uniforms,
+                             arraysize(shader_uniforms),
+                             arraysize(locations),
+                             locations,
+                             using_bind_uniform,
+                             base_uniform_index);
+
+  sampler_location_ = locations[0];
+  DCHECK_NE(sampler_location_, -1);
+
+  background_color_location_ = locations[1];
+  DCHECK_NE(background_color_location_, -1);
+}
+
+std::string FragmentShaderTexture::GetShaderString(
     TexCoordPrecision precision) const {
   return FRAGMENT_SHADER(
     precision mediump float;
     varying TexCoordPrecision vec2 v_texCoord;
     varying float v_alpha;
     uniform sampler2D s_texture;
+    uniform vec4 background_color;
     void main() {
       vec4 texColor = texture2D(s_texture, v_texCoord);
+      texColor += background_color * (1.0 - texColor.a);
       gl_FragColor = texColor * v_alpha;
     }
   );  // NOLINT(whitespace/parens)
 }
 
-std::string FragmentShaderRGBATexPremultiplyAlpha::GetShaderString(
+std::string FragmentShaderNonPremulTexture::GetShaderString(
     TexCoordPrecision precision) const {
   return FRAGMENT_SHADER(
     precision mediump float;
     varying TexCoordPrecision vec2 v_texCoord;
     varying float v_alpha;
     uniform sampler2D s_texture;
+    uniform vec4 background_color;
     void main() {
       vec4 texColor = texture2D(s_texture, v_texCoord);
       texColor.rgb *= texColor.a;
+      texColor += background_color * (1.0 - texColor.a);
       gl_FragColor = texColor * v_alpha;
     }
   );  // NOLINT(whitespace/parens)