Preserve page resize information when main frame is remote

third_party/WebKit/Source/web/WebViewImpl.cpp

Index: third_party/WebKit/Source/web/WebViewImpl.cpp
diff --git a/third_party/WebKit/Source/web/WebViewImpl.cpp b/third_party/WebKit/Source/web/WebViewImpl.cpp
index 7be5f1006676c7800988794aeae343f3fe494fa6..1cc400e66b4c5ae75a95c91ad45cce6e516e14bc 100644
--- a/third_party/WebKit/Source/web/WebViewImpl.cpp
+++ b/third_party/WebKit/Source/web/WebViewImpl.cpp
@@ -1902,13 +1902,12 @@ TopControls& WebViewImpl::topControls()
 
 void WebViewImpl::resizeViewWhileAnchored(FrameView* view)
 {
-    // FIXME: TextAutosizer does not yet support out-of-process frames.
-    if (mainFrameImpl() && mainFrameImpl()->frame()->isLocalFrame()) {
+    ASSERT(mainFrameImpl() && mainFrameImpl()->frame()->isLocalFrame());
+
+    {
         // Avoids unnecessary invalidations while various bits of state in TextAutosizer are updated.
         TextAutosizer::DeferUpdatePageInfo deferUpdatePageInfo(page());
         performResize();
-    } else {
-        performResize();
     }
 
     m_fullscreenController->updateSize();
@@ -1923,6 +1922,17 @@ void WebViewImpl::resize(const WebSize& newSize)
     if (m_shouldAutoResize || m_size == newSize)
         return;
 
+    if (page()->mainFrame() && !page()->mainFrame()->isLocalFrame()) {
+        // Viewport resize for a remote main frame does not require any
+        // particular action, but the state needs to reflect the correct size
+        // so that it can be used for initalization if the main frame gets
+        // swapped to a LocalFrame at a later time.
+        m_size = newSize;
+        pageScaleConstraintsSet().didChangeViewSize(m_size);

[bokan, 2016/01/11 18:18:58]

Is this call to didChangeViewSize actually needed to make your case work?
pageScaleConstraintsSet is responsible for calculating min/max page scales and
layout width. I doubt it'll work as expected since it also needs the content
width which a remote process wont have, so unless you needed this I'd remove it.

[kenrb, 2016/01/11 20:50:26]

The original test case on https://crbug.com/526211 results in a page being
rendered with incorrect size without this line. When we are swapping from remote
to a local main frame we don't necessarily get a resize after the swap has
completed, so not updating the pageScaleConstraintsSet on the resize that we get
before the frame swap still affects rendering.

[bokan, 2016/01/11 20:52:53]

Ok, sgtm

+        page()->frameHost().visualViewport().setSize(m_size);
+        return;
+    }
+
     WebLocalFrameImpl* mainFrame = mainFrameImpl();
     if (!mainFrame)
         return;