Reviewed by Dumitru Daniliuc.

        Decouple Blob from ScriptExecutionContext.
        https://bugs.webkit.org/show_bug.cgi?id=45410

        - Removed ScriptExecutionContext pointers from Blob and File constructors.
        - Removed ScriptExecutionContext's collection of Blobs instance in that context.
        - Refactored BlobURL to make a distinction between 'public' blob urls and 'internal'
          urls that are used solely as identifiers. The former requires a SecurityOrigin to
          to manufacture, the latter does not.
        - Added a constant and accessor for the blob protocol scheme on the BlobURL class.

        No new tests are added since this is a cleanup.

        * bindings/js/SerializedScriptValue.cpp:
        (WebCore::CloneDeserializer::readFile):
        (WebCore::CloneDeserializer::readTerminal):
        * bindings/v8/SerializedScriptValue.cpp:
        (WebCore::ZigZag::Reader::readBlob):
        (WebCore::ZigZag::Reader::readFile):
        (WebCore::ZigZag::Reader::readFileList):
        * dom/ScriptExecutionContext.cpp:
        (WebCore::ScriptExecutionContext::~ScriptExecutionContext):
        (WebCore::ScriptExecutionContext::createPublicBlobURL):
        (WebCore::ScriptExecutionContext::revokePublicBlobURL):
        * dom/ScriptExecutionContext.h:
        * fileapi/Blob.cpp:
        (WebCore::Blob::Blob):
        (WebCore::Blob::~Blob):
        (WebCore::Blob::slice):
        * fileapi/Blob.h:
        (WebCore::Blob::create):
        (WebCore::Blob::url):
        * fileapi/Blob.idl:
        * fileapi/BlobBuilder.cpp:
        (WebCore::BlobBuilder::getBlob):
        * fileapi/BlobBuilder.h:
        * fileapi/BlobBuilder.idl:
        * fileapi/BlobURL.cpp:
        (WebCore::BlobURL::createPublicURL):
        (WebCore::BlobURL::createInternalURL):
        (WebCore::BlobURL::getOrigin):
        (WebCore::BlobURL::getIdentifier):
        (WebCore::BlobURL::createBlobURL):
        * fileapi/BlobURL.h:
        (WebCore::BlobURL::blobProtocol):
        (WebCore::BlobURL::BlobURL):
        * fileapi/File.cpp:
        (WebCore::File::File):
        * fileapi/File.h:
        (WebCore::File::create):
        * fileapi/FileReader.cpp: Register a public url to perform the read.
        (WebCore::FileReader::cleanup):
        (WebCore::FileReader::start):
        (WebCore::FileReader::didFinishLoading):
        (WebCore::FileReader::failed):
        * fileapi/FileReader.h: Added m_urlForReading data member.
        * fileapi/FileReaderSync.cpp:
        (WebCore::FileReaderSync::read): Register a public url to perform the read.
        * fileapi/ThreadableBlobRegistry.cpp:
        (WebCore::ThreadableBlobRegistry::registerBlobURL):
        (WebCore::ThreadableBlobRegistry::unregisterBlobURL):
        * fileapi/ThreadableBlobRegistry.h:
        * html/HTMLInputElement.cpp:
        (WebCore::HTMLInputElement::appendFormData):
        (WebCore::HTMLInputElement::setFileListFromRenderer):
        * page/SecurityOrigin.cpp: Use BlobURL.blobProtocol().
        (WebCore::SecurityOrigin::create):
        (WebCore::SecurityOrigin::canRequest):
        (WebCore::SecurityOrigin::canDisplay):
        * platform/chromium/ClipboardChromium.cpp:
        (WebCore::ClipboardChromium::files):
        * platform/gtk/ClipboardGtk.cpp:
        (WebCore::ClipboardGtk::files):
        * platform/mac/ClipboardMac.mm:
        (WebCore::ClipboardMac::files):
        * platform/win/ClipboardWin.cpp:
        (WebCore::ClipboardWin::files):

git-svn-id: http://svn.webkit.org/repository/webkit/trunk@67208 268f45cc-cd09-0410-ab3c-d52691b4dbfc