added support for PLS path rendering

src/gpu/gl/GrGLGpu.h

Index: src/gpu/gl/GrGLGpu.h
diff --git a/src/gpu/gl/GrGLGpu.h b/src/gpu/gl/GrGLGpu.h
index 255952020383a6c432c97916f62986987fe6e1f2..e8ea226ad44f38fdd4804fba3ece572a996c9c53 100644
--- a/src/gpu/gl/GrGLGpu.h
+++ b/src/gpu/gl/GrGLGpu.h
@@ -134,6 +134,8 @@ public:
 
     void drawDebugWireRect(GrRenderTarget*, const SkIRect&, GrColor) override;
 
+    void performFlushWorkaround() override;
+
 private:
     GrGLGpu(GrGLContext* ctx, GrContext* context);
 
@@ -220,6 +222,11 @@ private:
                                       const SkIRect& srcRect,
                                       const SkIPoint& dstPoint);
 
+    void stampRectUsingProgram(GrGLuint program, const SkRect& bounds, GrGLint posXformUniform, 
+                               GrGLuint arrayBuffer);
+
+    void setupPixelLocalStorage(const DrawArgs& args);
+
     static bool BlendCoeffReferencesConstant(GrBlendCoeff coeff);
 
     class ProgramCache : public ::SkNoncopyable {
@@ -341,6 +348,8 @@ private:
     void createWireRectProgram();
     void createUnitRectBuffer();
 
+    void createPLSSetupProgram();
+
     // GL program-related state
     ProgramCache*               fProgramCache;
 
@@ -551,6 +560,15 @@ private:
         }
     }
 
+    struct {
+        GrGLuint    fProgram;
+        GrGLint     fPosXformUniform;
+        GrGLuint    fArrayBuffer;
+    } fPLSSetupProgram;
+
+    bool fHWPLSEnabled;
+    bool fPLSHasBeenUsed = false;

[bsalomon, 2016/01/21 21:54:08]

Hm.. we don't use this type of init anywhere else. Not opposed but for
consistency, can we go with init in the constructor for now?

+
     typedef GrGpu INHERITED;
     friend class GrGLPathRendering; // For accessing setTextureUnit.
 };