Initial version of external_oes texture support and unit test

include/gpu/gl/SkGLContext.h

Index: include/gpu/gl/SkGLContext.h
diff --git a/include/gpu/gl/SkGLContext.h b/include/gpu/gl/SkGLContext.h
index 75cfcfee045896013f7c6dae3239ecc2e4f96683..3420a47973228594d4d1f8f6fc24cca9df685f3c 100644
--- a/include/gpu/gl/SkGLContext.h
+++ b/include/gpu/gl/SkGLContext.h
@@ -14,8 +14,9 @@
 /**
  * Create an offscreen opengl context with an RGBA8 / 8bit stencil FBO.
  * Provides a GrGLInterface struct of function pointers for the context.
+ * This class is intended for Skia's testing needs and not for general
+ * use.
  */
-
 class SK_API SkGLContext : public SkRefCnt {
 public:
     ~SkGLContext() override;
@@ -36,6 +37,16 @@ public:
 
     void makeCurrent() const;
 
+    /** Used for testing EGLImage integration. Take a GL_TEXTURE_2D and wraps it in an EGL Image */
+    virtual GrEGLImage texture2DToEGLImage(GrGLuint /*texID*/) const { return 0; }
+    virtual void destroyEGLImage(GrEGLImage) const {}
+
+    /**
+     * Used for testing EGLImage integration. Takes a EGLImage and wraps it in a
+     * GL_TEXTURE_EXTERNAL_OES.
+     */
+    virtual GrGLuint eglImageToExternalTexture(GrEGLImage) const { return 0; }
+
     /**
      * The only purpose of this function it to provide a means of scheduling
      * work on the GPU (since all of the subclasses create primary buffers for
@@ -59,6 +70,12 @@ public:
      */
     void testAbandon();
 
+    /**
+     * Creates a new GL context of the same type and makes the returned context current
+     * (if not null).
+     */
+    virtual SkGLContext* createNew() const { return nullptr; }
+
     class GLFenceSync;  // SkGpuFenceSync implementation that uses the OpenGL functionality.
 
 protected: