Adding public API method on SkImage for extracting the GPU texture handle.

TEST=Surface unit test

Review URL: https://codereview.chromium.org/14646007

git-svn-id: http://skia.googlecode.com/svn/trunk@8945 2bbb7eff-a529-9590-31e7-b0007b416f81
diff --git a/src/image/SkImage_Gpu.cpp b/src/image/SkImage_Gpu.cpp
index f531a77..451ad07 100644
--- a/src/image/SkImage_Gpu.cpp
+++ b/src/image/SkImage_Gpu.cpp
@@ -21,6 +21,7 @@
     virtual ~SkImage_Gpu();
 
     virtual void onDraw(SkCanvas*, SkScalar x, SkScalar y, const SkPaint*) SK_OVERRIDE;
+    virtual GrTexture* onGetTexture() SK_OVERRIDE;
 
     GrTexture* getTexture() { return fTexture; }
 
@@ -56,6 +57,10 @@
     canvas->drawBitmap(fBitmap, x, y, paint);
 }
 
+GrTexture* SkImage_Gpu::onGetTexture() {
+    return fTexture;
+}
+
 void SkImage_Gpu::setTexture(GrTexture* texture) {
 
     if (texture == fTexture) {