Add <link rel=preconnect> support to the HTMLPreloadScanner

Source/core/core.gypi

 {
     'includes': [
         'core_generated.gypi',
     ],
     'variables': {
         # Files for which bindings (.cpp and .h files) will be generated
         'core_idl_files': [
             'animation/KeyframeEffect.idl',
             'animation/EffectModel.idl',
             'animation/AnimationEffectReadOnly.idl',
@@ skipping 1730 matching lines @@
             'loader/LinkLoader.cpp',
             'loader/LinkLoader.h',
             'loader/LinkLoaderClient.h',
             'loader/MixedContentChecker.cpp',
             'loader/MixedContentChecker.h',
             'loader/NavigationPolicy.cpp',
             'loader/NavigationPolicy.h',
             'loader/NavigationScheduler.cpp',
             'loader/PingLoader.cpp',
             'loader/PingLoader.h',
+            'loader/Preconnecter.cpp',

[Mike West, 2015/06/02 11:18:33]

Nit: Preconnect_o_r.

+            'loader/Preconnecter.h',
             'loader/PrerenderHandle.cpp',
             'loader/PrerenderHandle.h',
             'loader/PrerendererClient.cpp',
             'loader/PrerendererClient.h',
             'loader/ProgressTracker.cpp',
             'loader/SinkDocument.cpp',
             'loader/SinkDocument.h',
             'loader/TextResourceDecoderBuilder.cpp',
             'loader/TextResourceDecoderBuilder.h',
             'loader/TextTrackLoader.cpp',
@@ skipping 2156 matching lines @@
             'style/ComputedStyleTest.cpp',
             'style/OutlineValueTest.cpp',
             'style/SVGComputedStyleTest.cpp',
             'testing/PrivateScriptTestTest.cpp',
             'timing/MemoryInfoTest.cpp',
             'workers/WorkerThreadTest.cpp',
             'xml/parser/SharedBufferReaderTest.cpp',
         ],
     }
 }