new image from backend desc

BUG=485243

Review URL: https://codereview.chromium.org/1121813002
diff --git a/include/core/SkImage.h b/include/core/SkImage.h
index ebc9a29..7128f6e 100644
--- a/include/core/SkImage.h
+++ b/include/core/SkImage.h
@@ -64,6 +64,24 @@
      */
     static SkImage* NewFromData(SkData* data);
 
+    /**
+     *  Create a new image from the specified descriptor. Note - the caller is responsible for
+     *  managing the lifetime of the underlying platform texture.
+     *
+     *  Will return NULL if the specified descriptor is unsupported.
+     */
+    static SkImage* NewFromTexture(GrContext*, const GrBackendTextureDesc&,
+                                   SkAlphaType = kPremul_SkAlphaType);
+
+    /**
+     *  Create a new image by copying the pixels from the specified descriptor. No reference is
+     *  kept to the original platform texture.
+     *
+     *  Will return NULL if the specified descriptor is unsupported.
+     */
+    static SkImage* NewFromTextureCopy(GrContext*, const GrBackendTextureDesc&,
+                                       SkAlphaType = kPremul_SkAlphaType);
+
     int width() const { return fWidth; }
     int height() const { return fHeight; }
     uint32_t uniqueID() const { return fUniqueID; }