Remove RenderLayer::AncestorDependentPropertyCache

This CL removes RenderLayer's AncestorDependentPropertyCache. I had asked
vollick to add this cache because I was worried about the costs of walking up
the tree during the compositing update. Discussing this topic with more people,
I now don't think this is a real problem. Instead, this cache creates a
different problem, which is that clearAncestorDependentPropertyCacheRecursive
shows up on profiles of pages that have a large number of RenderLayers.

In the future, if we need to compute this information more efficiently, we can
compute it while walking down the tree in the CompositingPropertyUpdater. As a
proof-of-concept, Elliot and I wrote some code that computes the
ancestorCompositedScrollingLayer while walking down the tree. However, I don't
think it's worth adding that code to the system until we see this issue on a
profile.

R=esprehn@chromium.org

Review URL: https://codereview.chromium.org/229723004

git-svn-id: svn://svn.chromium.org/blink/trunk@171108 bbb929c8-8fbe-4397-9dbb-9b2b20218538
Fix incorrect dictionary lookup popover positioning when the web content's
scroll position is not at the top.
We were adjusting for the scroll position twice.

TEST=Navigate to a scrollable web page and scroll down so that the scroll position is no longer on top. Hover the cursor over a word and either tap with 3 fingers or invoke Cmd+Ctrl+D. A dictionary popover should appear next to the selected word where before the fix it was showing at the wrong location. Note: this feature requires Mac OS 10.8 or newer.

Review URL: https://codereview.chromium.org/226333002

git-svn-id: svn://svn.chromium.org/blink/trunk@171109 bbb929c8-8fbe-4397-9dbb-9b2b20218538