Introduce Promises.

Source/core/core.gypi

 {
     'variables': {
         'core_idl_files': [
             'css/CSS.idl',
             'css/CSSCharsetRule.idl',
             'css/CSSFontFaceLoadEvent.idl',
             'css/CSSFontFaceRule.idl',
             'css/CSSHostRule.idl',
             'css/CSSImportRule.idl',
             'css/CSSMediaRule.idl',
@@ skipping 72 matching lines @@
             'dom/NodeFilter.idl',
             'dom/NodeIterator.idl',
             'dom/NodeList.idl',
             'dom/Notation.idl',
             'dom/OverflowEvent.idl',
             'dom/PageTransitionEvent.idl',
             'dom/ParentNode.idl',
             'dom/PopStateEvent.idl',
             'dom/ProcessingInstruction.idl',
             'dom/ProgressEvent.idl',
+            'dom/Promise.idl',
+            'dom/PromiseResolver.idl',
             'dom/Range.idl',
             'dom/RequestAnimationFrameCallback.idl',
             'dom/ResourceProgressEvent.idl',
             'dom/SecurityPolicyViolationEvent.idl',
             'dom/StringCallback.idl',
             'dom/Text.idl',
             'dom/TextEvent.idl',
             'dom/Touch.idl',
             'dom/TouchEvent.idl',
             'dom/TouchList.idl',
@@ skipping 1749 matching lines @@
             'dom/PendingScript.cpp',
             'dom/PopStateEvent.cpp',
             'dom/PopStateEvent.h',
             'dom/Position.cpp',
             'dom/PositionIterator.cpp',
             'dom/PositionIterator.h',
             'dom/ProcessingInstruction.cpp',
             'dom/ProcessingInstruction.h',
             'dom/ProgressEvent.cpp',
             'dom/ProgressEvent.h',
+            'dom/Promise.h',
+            'dom/PromiseResolver.h',
             'dom/PseudoElement.cpp',
             'dom/QualifiedName.cpp',
             'dom/Range.cpp',
             'dom/RawDataDocumentParser.h',
             'dom/RequestAnimationFrameCallback.h',
             'dom/ResourceProgressEvent.cpp',
             'dom/ResourceProgressEvent.h',
             'dom/ScopedEventQueue.cpp',
             'dom/ScopedEventQueue.h',
             'dom/ScriptElement.cpp',
@@ skipping 1823 matching lines @@
                 'bison_exe': 'bison',
                 # We specify a preprocess so it happens locally and won't get
                 # distributed to goma.
                 # FIXME: /usr/bin/gcc won't exist on OSX forever. We want to
                 # use /usr/bin/clang once we require Xcode 4.x.
                 'preprocessor': '--preprocessor "/usr/bin/gcc -E -P -x c++"'
               }],
          ],
     }
 }