Fix visual viewport for OOPIF.

third_party/WebKit/Source/web/WebFrameWidgetImpl.cpp

Index: third_party/WebKit/Source/web/WebFrameWidgetImpl.cpp
diff --git a/third_party/WebKit/Source/web/WebFrameWidgetImpl.cpp b/third_party/WebKit/Source/web/WebFrameWidgetImpl.cpp
index 4f24ed063bc42c869615d57ad344522df082ad49..8e58307f7bafde8aa7b6b1577350af8b1e968448 100644
--- a/third_party/WebKit/Source/web/WebFrameWidgetImpl.cpp
+++ b/third_party/WebKit/Source/web/WebFrameWidgetImpl.cpp
@@ -35,6 +35,7 @@
 #include "core/editing/FrameSelection.h"
 #include "core/editing/InputMethodController.h"
 #include "core/editing/PlainTextRange.h"
+#include "core/frame/FrameHost.h"
 #include "core/frame/FrameView.h"
 #include "core/frame/RemoteFrame.h"
 #include "core/frame/Settings.h"
@@ -199,7 +200,8 @@ void WebFrameWidgetImpl::sendResizeEventAndRepaint()
 
 void WebFrameWidgetImpl::resizeVisualViewport(const WebSize& newSize)
 {
-    // FIXME: Implement visual viewport for out-of-process iframes.
+    page()->frameHost().visualViewport().setSize(newSize);
+    page()->frameHost().visualViewport().clampToBoundaries();

[alexmos, 2016/03/26 00:00:48]

Note that I didn't have to add any plumbing for sending resize messages for
OOPIFs, as this kind of happens for free today.  Here's the flow of events when
you resize the window:
- ViewMsg_Resize is sent to main frame's renderer
- eventually, this hits FrameView::frameRectsChanged(), which goes and calls
frameRectsChanged on its children and hits RemoteFrameView::frameRectsChanged()
for an OOPIF.
- that sends FrameHostMsg_FrameRectChanged back to browser via the proxy.
- browser calls CrossProcessFrameConnector::SetRect()
- that gets to RenderWidgetHostViewChildFrame::SetSize(), which calls
RenderWidgetHostImpl::WasResized().
- before this CL, no resize message would be sent because ResizeParams stayed
the same.  But now that RenderWidgetHostViewChildFrame::GetVisibleViewportSize()
returns a different viewport size (due to window resize), this proceeds to send
ViewMsg_Resize to the subframe widget.
- RenderWidget::Resize() calls WebWidget::resizeVisualViewport(), which ends up
here.

We could probably optimize this in the future to avoid the extra roundtrip.

[kenrb, 2016/03/31 17:41:58]

Eventually we might want to change some of the resizing behavior to Page
messages. It doesn't seem like the visual viewport should be set once for each
local root. This isn't a high priority, but I might suggest filing a bug for
that so we can get around to it at some point.

[alexmos, 2016/03/31 23:03:47]

Good point.  I suppose this means that in cases like A-B-A we might have some
redundant updates.  I filed https://crbug.com/599688 and referenced here.

 }
 
 void WebFrameWidgetImpl::updateMainFrameLayoutSize()