Adding YUVA support for enabling Alpha Playback

cc/output/shader.cc

Index: cc/output/shader.cc
diff --git a/cc/output/shader.cc b/cc/output/shader.cc
index d70352f58c38e937285cb32e0e2aaa20eeeba561..474e539b79d979dc7daa3e1bea28014b8ddf5a17 100644
--- a/cc/output/shader.cc
+++ b/cc/output/shader.cc
@@ -913,6 +913,83 @@ std::string FragmentShaderYUVVideo::GetShaderString() const {
   );
 }
 
+FragmentShaderYUVAVideo::FragmentShaderYUVAVideo()
+    : y_texture_location_(-1)
+    , u_texture_location_(-1)
+    , v_texture_location_(-1)
+    , a_texture_location_(-1)
+    , alpha_location_(-1)
+    , yuv_matrix_location_(-1)
+    , yuv_adj_location_(-1)
+{
+}
+
+void FragmentShaderYUVAVideo::Init(WebGraphicsContext3D* context,
+                                   unsigned program,
+                                   bool using_bind_uniform,
+                                   int* base_uniform_index)
+{
+    static const char* shader_uniforms[] = {
+        "y_texture",
+        "u_texture",
+        "v_texture",
+        "a_texture",
+        "alpha",
+        "cc_matrix",
+        "yuv_adj",
+    };
+    int locations[7];
+
+    GetProgramUniformLocations(context,
+                               program,
+                               shader_uniforms,
+                               arraysize(shader_uniforms),
+                               arraysize(locations),
+                               locations,
+                               using_bind_uniform,
+                               base_uniform_index);
+
+    y_texture_location_ = locations[0];
+    u_texture_location_ = locations[1];
+    v_texture_location_ = locations[2];
+    a_texture_location_ = locations[3];
+    alpha_location_ = locations[4];
+    yuv_matrix_location_ = locations[5];
+    yuv_adj_location_ = locations[6];
+
+    DCHECK(y_texture_location_ != -1 && u_texture_location_ != -1 &&
+           v_texture_location_ != -1 && a_texture_location_ != -1 &&
+           alpha_location_ != -1 && yuv_matrix_location_ != -1 &&
+           yuv_adj_location_ != -1);
+}
+
+std::string FragmentShaderYUVAVideo::GetShaderString() const
+{
+    return SHADER(
+        precision mediump float;
+        precision mediump int;
+        varying vec2 y_texCoord;
+        varying vec2 uv_texCoord;
+        uniform sampler2D y_texture;
+        uniform sampler2D u_texture;
+        uniform sampler2D v_texture;
+        uniform sampler2D a_texture;
+        uniform float alpha;
+        uniform vec3 yuv_adj;
+        uniform mat3 cc_matrix;
+        void main()
+        {
+            float y_raw = texture2D(y_texture, y_texCoord).x;
+            float u_unsigned = texture2D(u_texture, uv_texCoord).x;
+            float v_unsigned = texture2D(v_texture, uv_texCoord).x;
+            float a_raw = texture2D(a_texture, y_texCoord).x;
+            vec3 yuv = vec3(y_raw, u_unsigned, v_unsigned) + yuv_adj;
+            vec3 rgb = cc_matrix * yuv;
+            gl_FragColor = vec4(rgb, float(1)) * (a_raw * alpha);
+        }
+    );
+}
+
 FragmentShaderColor::FragmentShaderColor()
     : color_location_(-1) {}