Display anonymous regions in DRT

This patch allows displaying the anonymous region inside a block with flow-from style set.

Before the patch:
  RenderRegion {DIV} at (200,200) size 52x52 [border: (1px solid #000000)]
After the patch:
  RenderBlock (positioned) {DIV} at (200,200) size 52x52 [border: (1px solid #000000)]
    RenderNamedFlowFragment at (1,1) size 50x50

Before the patch:
  Flow Threads
    Thread with flow-name 'article'
      Regions for flow 'article'
      RenderRegion {DIV} #region_1
      RenderRegion {DIV} #region_2

After the patch:
  Named flows
    Named flow 'article'
      Regions for named flow 'article'
        RenderNamedFlowFragment (anonymous child of {DIV} #region_1)
        RenderNamedFlowFragment (anonymous child of {DIV} #region_2)

BUG=321217

Review URL: https://codereview.chromium.org/79433004

git-svn-id: svn://svn.chromium.org/blink/trunk@162606 bbb929c8-8fbe-4397-9dbb-9b2b20218538
Make window.frameElement use the creation context of the parent frame

Previously, accessing window.frameElement inside an <iframe> would cause
the iframe wrapper to use the prototype from its own context, rather
than the context of the frame it's in. This patch fixes that and is
consistent with Firefox and IE (haven't tested on Safari).

This patch doesn't change the cross-origin policy check, which is
covered by an existing test:
http/tests/security/cross-frame-access-frameelement.html

BUG=321032

Review URL: https://codereview.chromium.org/82653003

git-svn-id: svn://svn.chromium.org/blink/trunk@162607 bbb929c8-8fbe-4397-9dbb-9b2b20218538
Improve HTMLMeterElement exception messages.

BUG=270033

Review URL: https://codereview.chromium.org/83473002

git-svn-id: svn://svn.chromium.org/blink/trunk@162608 bbb929c8-8fbe-4397-9dbb-9b2b20218538