Issue #1620 - Use Intrinsic Aspect Ratio for Images

https://bugzilla.mozilla.org/show_bug.cgi?id=1547231
https://bugzilla.mozilla.org/show_bug.cgi?id=1559094
https://bugzilla.mozilla.org/show_bug.cgi?id=1633434
https://bugzilla.mozilla.org/show_bug.cgi?id=1565690
https://bugzilla.mozilla.org/show_bug.cgi?id=1602047

Make use of Aspect Ratios in Image frames before Images are loaded.
- Check for width and height HTML properties and create a ratio with them.
- Overwrite HTML size values with actual image dimensions on load.
- Collapse any frames with srcless images.

Comments:
dom/html/nsGenericHTMLElement.cpp:1483
layout/generic/nsImageFrame.cpp:289

layout/generic/nsImageFrame.h

@@ -273,21 +273,19 @@ private:
   void GetDocumentCharacterSet(nsACString& aCharset) const;
   bool ShouldDisplaySelection();
 
+  // Whether the image frame should use the mapped aspect ratio from width=""
+  // and height="".
+  bool ShouldUseMappedAspectRatio() const;
+
   /**
    * Recalculate mIntrinsicSize from the image.
-   *
-   * @return whether aImage's size did _not_
-   *         match our previous intrinsic size.
    */
-  bool UpdateIntrinsicSize(imgIContainer* aImage);
+  bool UpdateIntrinsicSize();
 
   /**
    * Recalculate mIntrinsicRatio from the image.
-   *
-   * @return whether aImage's ratio did _not_
-   *         match our previous intrinsic ratio.
    */
-  bool UpdateIntrinsicRatio(imgIContainer* aImage);
+  bool UpdateIntrinsicRatio();
 
   /**
    * This function calculates the transform for converting between
@@ -307,6 +305,12 @@ private:
    */
   bool IsPendingLoad(imgIRequest* aRequest) const;
 
+  /**
+   * Updates mImage based on the current image request (cannot be null), and the
+   * image passed in (can be null), and invalidate layout and paint as needed.
+   */
+  void UpdateImage(imgIRequest* aRequest, imgIContainer* aImage);
+
   /**
    * Function to convert a dirty rect in the source image to a dirty
    * rect for the image frame.