Disable SVG Fonts in CSS on all platforms except GDI Windows (XP, Vista)

This patch disables SVG fonts everywhere except GDI platforms, per [1].
The patch itself is straightforward: the SVGFontsOnNonGDIPlatforms
runtime enabled feature has been added but is disabled by default.

TestExpectations has been updated with the usual mass of rebaselines.
coords-dom-02-f.svg has been marked as no longer failing.

A brand new test has been added to test the fallback code. This test is
marked as failing on XP (we have no Vista bots).

[1] https://groups.google.com/a/chromium.org/d/msg/blink-dev/pYbbUcYvlYY/LQvFvM8KZZEJ

BUG=242735

Review URL: https://codereview.chromium.org/360203002

git-svn-id: svn://svn.chromium.org/blink/trunk@177785 bbb929c8-8fbe-4397-9dbb-9b2b20218538
Revert of Update XMLHttpRequest forbidden header names. (https://codereview.chromium.org/378183003/)

Reason for revert:
Caused browser_tests failure
http://build.chromium.org/p/chromium.webkit/builders/Linux%20Tests/builds/37851

    OutOfProcessPPAPITest.URLLoader3
    PPAPINaClGLibcTest.URLLoader3
    PPAPINaClNewlibTest.URLLoader3
    PPAPINaClPNaClTest.URLLoader3
    PPAPITest.URLLoader3


Original issue's description:
> Update XMLHttpRequest forbidden header names.
> 
> See http://fetch.spec.whatwg.org/#forbidden-header-name .
> 
> BUG=373120
> 
> Committed: https://src.chromium.org/viewvc/blink?view=rev&revision=177762

TBR=abarth@chromium.org,yhirano@chromium.org
NOTREECHECKS=true
NOTRY=true
BUG=373120

Review URL: https://codereview.chromium.org/385493002

git-svn-id: svn://svn.chromium.org/blink/trunk@177786 bbb929c8-8fbe-4397-9dbb-9b2b20218538
Fold ImageLoader::updateFromElementIgnoringPreviousError into updateFromElement

This CL is just a refactor that should have no functional impact. It is done as ground work in order to later add yet a third mode to updateFromElement.

BUG=

Review URL: https://codereview.chromium.org/378163002

git-svn-id: svn://svn.chromium.org/blink/trunk@177787 bbb929c8-8fbe-4397-9dbb-9b2b20218538