[Blink] Don't center images in Android WebViews

third_party/WebKit/Source/core/html/ImageDocument.cpp

 /*
  * Copyright (C) 2006, 2007, 2008, 2010 Apple Inc. All rights reserved.
  *
  * Redistribution and use in source and binary forms, with or without
  * modification, are permitted provided that the following conditions
  * are met:
  * 1. Redistributions of source code must retain the above copyright
  *    notice, this list of conditions and the following disclaimer.
  * 2. Redistributions in binary form must reproduce the above copyright
  *    notice, this list of conditions and the following disclaimer in the
@@ skipping 30 matching lines @@
 #include "core/html/HTMLDivElement.h"
 #include "core/html/HTMLHeadElement.h"
 #include "core/html/HTMLHtmlElement.h"
 #include "core/html/HTMLImageElement.h"
 #include "core/html/HTMLMetaElement.h"
 #include "core/layout/LayoutObject.h"
 #include "core/loader/DocumentLoader.h"
 #include "core/loader/FrameLoader.h"
 #include "core/loader/FrameLoaderClient.h"
 #include "core/loader/resource/ImageResource.h"
+#include "core/page/Page.h"
 #include "platform/HostWindow.h"
 #include "wtf/text/StringBuilder.h"
 #include <limits>
 
 using namespace std;
 
 namespace {
 
 // The base square size is set to 10 because it rounds nicely for both the
 // minimum scale (0.1) and maximum scale (5.0).
@@ skipping 526 matching lines @@
     if (isStopped()) {
       m_imageElement = nullptr;
       return nullptr;
     }
   }
 
   return m_imageElement->cachedImageResourceForImageDocument();
 }
 
 bool ImageDocument::shouldShrinkToFit() const {
-  return frame()->isMainFrame();
+  bool isWrapContentWebView =
+      page() ? page()->settings().getForceZeroLayoutHeight() : false;

[pdr., 2017/01/19 03:17:32]

Is getForceZeroLayoutHeight causing the height to be zero which causes the
infinite loop of window size changes? Or is getForceZeroLayoutHeight only used
as a "isWebview" check?

[aelias_OOO_until_Jul13, 2017/01/19 03:53:07]

It's used as isWebView (_in_WRAP_CONTENT_mode).  The reason in the first place
for the settings is because a lot of the rest of Blink layout is prone to the
same infinite loop of window size changes, and forcing the layout height to zero
proves a nice universal mitigation.  The code in this file uses visible height
instead of layout height so it needs a more explicit check.

[pdr., 2017/01/19 05:04:27]

Could we just add an isWebView() function instead of getWideViewportQuirkEnabled
and getForceZeroLayoutHeight? I see several of these calls throughout Blink.
That's out of scope for this patch though.

Can we add a comment here though? Something similar to the change description
like "WebView automatically resizes to match the contents which will cause an
infinite loop as the contents then resize to match the window. To prevent this,
we disable shrinking to fit for WebViews"

+  return frame()->isMainFrame() && !isWrapContentWebView;
 }
 
 DEFINE_TRACE(ImageDocument) {
   visitor->trace(m_divElement);
   visitor->trace(m_imageElement);
   HTMLDocument::trace(visitor);
 }
 
 // --------
 
@@ skipping 11 matching lines @@
 }
 
 bool ImageEventListener::operator==(const EventListener& listener) const {
   if (const ImageEventListener* imageEventListener =
           ImageEventListener::cast(&listener))
     return m_doc == imageEventListener->m_doc;
   return false;
 }
 
 }  // namespace blink