Change GR_COMPRESS_ALPHA_MASK from compile-time flag to run-time flag

include/gpu/GrContext.h

Index: include/gpu/GrContext.h
diff --git a/include/gpu/GrContext.h b/include/gpu/GrContext.h
index 39f5be728f85b171920d841b842f69791905fa77..f5f0930bb0513d59504bb2c57ffda5c4102255a9 100644
--- a/include/gpu/GrContext.h
+++ b/include/gpu/GrContext.h
@@ -49,10 +49,15 @@ class SK_API GrContext : public SkRefCnt {
 public:
     SK_DECLARE_INST_COUNT(GrContext)
 
+    struct Options {
+        Options();
+        bool fDrawPathToCompressedTexture;

[bsalomon, 2014/08/11 19:00:47]

Should we label this field experimental or something? I imagine in the future we
will either always use it or not based on what the testing looks like.

[krajcevski, 2014/08/11 19:09:55]

Done.

+    };
+
     /**
      * Creates a GrContext for a backend context.
      */
-    static GrContext* Create(GrBackend, GrBackendContext);
+    static GrContext* Create(GrBackend, GrBackendContext, const Options* opts = NULL);
 
     virtual ~GrContext();
 
@@ -322,6 +327,14 @@ public:
      */
     void setMaxTextureSizeOverride(int maxTextureSizeOverride);
 
+    /**
+     *  This returns true if the underlying graphics device and system is
+     *  capable of drawing paths to compressed textures. This generally provides
+     *  a speedup on mobile devices with advanced GPUs, but it only gets turned
+     *  on when there is a clear speedup benefit.
+     */
+    bool supportsDrawPathToCompressedTexture() const;

[bsalomon, 2014/08/11 19:00:47]

Does this need to be public? It feels like we're exposing an implementation
detail that most users shouldn't care about.

[krajcevski, 2014/08/11 19:09:55]

I moved it to the "for internal use only" section.

+
     ///////////////////////////////////////////////////////////////////////////
     // Render targets
 
@@ -986,9 +999,10 @@ private:
     SkTDArray<CleanUpData>          fCleanUpData;
 
     int                             fMaxTextureSizeOverride;
+    bool                            fSupportsDrawPathToCompressed;
 
     GrContext(); // init must be called after the constructor.
-    bool init(GrBackend, GrBackendContext);
+    bool init(GrBackend, GrBackendContext, const Options& opts);
 
     void setupDrawBuffer();