Revert of GC plugin: consider references equal to raw pointers. (patchset #2 id:20001...

Revert of GC plugin: consider references equal to raw pointers. (patchset #2 id:20001 of https://codereview.chromium.org/1274403002/ )

Reason for revert:
Turned the clang/win tot bots red: http://build.chromium.org/p/chromium.fyi/builders/ClangToTWin/builds/2327/steps/compile/logs/stdio

..\..\third_party\WebKit\Source\core/css/parser/CSSSupportsParser.h(13,1) :  error: [blink-gc] Class 'CSSSupportsParser' contains invalid fields.
class CSSSupportsParser {
^
..\..\third_party\WebKit\Source\core/css/parser/CSSSupportsParser.h(31,5) :  note: [blink-gc] Stack-allocated field 'm_parser' declared here:
    CSSParserImpl& m_parser;
    ^

Original issue's description:
> GC plugin: consider references equal to raw pointers.
>
> Unmanaged raw pointers to managed(GC) classes aren't safe across GCs,
> hence fields with raw pointer types to such GCed classes are identified
> and reported as errors or warnings.
>
> Extend that checking to also apply to reference pointer types.
>
> R=haraken
> BUG=420515
>
> Committed: https://crrev.com/70fe23896f81cd66ba1a205b0336f91c64e3fa4e
> Cr-Commit-Position: refs/heads/master@{#342320}

TBR=oilpan-reviews@chromium.org,sigbjornf@opera.com
NOPRESUBMIT=true
NOTREECHECKS=true
NOTRY=true
BUG=420515

Review URL: https://codereview.chromium.org/1275383002

Cr-Commit-Position: refs/heads/master@{#342366}