Revert of Initial draft - modify ViewportAnchor to know about both inner and outer viewports. (patchset #11 id:200001 of https://codereview.chromium.org/556703005/)

Reason for revert:
The new test is failing on mac. Reverting for now so it can be investigated.

[  FAILED  ] PinchViewportTest.TestResizeAfterHorizontalScroll (39 ms)
[1471/1471] PinchViewportTest.TestResizeAfterHorizontalScroll (39 ms)
Retrying 2 tests (retry #3)
[ RUN      ] PinchViewportTest.TestResizeAfterVerticalScroll
../../third_party/WebKit/Source/web/tests/PinchViewportTest.cpp:251: Failure
Value of: (pinchViewport.visibleRect().size()).width()
Actual: 45.94595
Expected: (FloatSize(50, 25)).width()
Which is: 50
../../third_party/WebKit/Source/web/tests/PinchViewportTest.cpp:251: Failure
Value of: (pinchViewport.visibleRect().size()).height()
Actual: 22.972975
Expected: (FloatSize(50, 25)).height()
Which is: 25
../../third_party/WebKit/Source/web/tests/PinchViewportTest.cpp:253: Failure
Value of: (frame()->view()->scrollPosition()).y()
Actual: 638
Expected: (IntPoint(0, 625)).y()
Which is: 625
../../third_party/WebKit/Source/web/tests/PinchViewportTest.cpp:254: Failure
Value of: (pinchViewport.location()).y()
Actual: 62
Expected: (FloatPoint(0, 75)).y()
Which is: 75

Original issue's description:
> Fix pinch virtual viewport position after resize.
> 
> Associate the viewport anchor with the inner viewport.
> Adjust the inner and outer viewport positions after resize
> such that they both remain in their allowed range and the
> inner viewport origin scales proportionally within the
> outer viewport.
> 
> As a small cleanup, made the method ScrollView::scrollTo() protected.
> 
> BUG=364108
> 
> Committed: https://src.chromium.org/viewvc/blink?view=rev&revision=182365

TBR=leviw@chromium.org,aelias@chromium.org,bokan@chromium.org,timav@google.com,timav@chromium.org
NOTREECHECKS=true
NOTRY=true
BUG=364108

Review URL: https://codereview.chromium.org/597113002

git-svn-id: svn://svn.chromium.org/blink/trunk@182580 bbb929c8-8fbe-4397-9dbb-9b2b20218538