Remove GL-specific code from GMs and tests

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 e5cd7a9a9d1de3c1edf7723de98628eaa2880fef..f85f22fd616307b0ec5e965d23bd6863eeee6f91 100644
--- a/src/gpu/gl/GrGLGpu.h
+++ b/src/gpu/gl/GrGLGpu.h
@@ -108,9 +108,10 @@ public:
                           const GrPipeline&,
                           const GrBatchTracker&) const override;
 
-    const GrGLContext* glContextForTesting() const override {
-        return &this->glContext();
-    }
+    GrBackendObject createBackendTexture(void* pixels, int w, int h,
+                                         GrPixelConfig config) const override;
+    bool isBackendTexture(GrBackendObject id) const override;
+    void deleteBackendTexture(GrBackendObject id) const override;
 
 private:
     GrGLGpu(GrGLContext* ctx, GrContext* context);
@@ -265,7 +266,7 @@ private:
                            bool getSizedInternal,
                            GrGLenum* internalFormat,
                            GrGLenum* externalFormat,
-                           GrGLenum* externalType);
+                           GrGLenum* externalType) const;
     // helper for onCreateTexture and writeTexturePixels
     bool uploadTexData(const GrSurfaceDesc& desc,
                        bool isNewTexture,