Checking if frame is complete and access duration doesn't need a decode

Source/core/platform/graphics/ImageSource.h

Index: Source/core/platform/graphics/ImageSource.h
diff --git a/Source/core/platform/graphics/ImageSource.h b/Source/core/platform/graphics/ImageSource.h
index 5c12199af04991eab96c4f714c7b0bbbd3f97307..045232c03ac8fbabbc6ccfb93644580865139bc1 100644
--- a/Source/core/platform/graphics/ImageSource.h
+++ b/Source/core/platform/graphics/ImageSource.h
@@ -127,9 +127,9 @@ public:
     // see comments on clear() above.
     PassNativeImagePtr createFrameAtIndex(size_t);
 
-    float frameDurationAtIndex(size_t);
-    bool frameHasAlphaAtIndex(size_t); // Whether or not the frame actually used any alpha.
-    bool frameIsCompleteAtIndex(size_t); // Whether or not the frame is completely decoded.
+    float frameDurationAtIndex(size_t) const;
+    bool frameHasAlphaAtIndex(size_t) const; // Whether or not the frame actually used any alpha.
+    bool frameIsCompleteAtIndex(size_t) const; // Whether or not the frame is fully received.
     ImageOrientation orientationAtIndex(size_t) const; // EXIF image orientation
 
     // Return the number of bytes in the decoded frame. If the frame is not yet