Add spell checking support (issue #137).

This includes:
- Red underline of misspelled words in html text areas.
- Right-click context menu options to correct the misspelled word.
- New CefBrowser::ReplaceMisspelling method for accepting a word replacement.
- Methods added to CefContextMenuParams for retrieving spelling-related information.
- Uses the unified text checker when auto-correct is not enabled to match Google Chrome behavior.
- On Windows and Linux a hunspell dictionary file will be downloaded to the "<cache_path>/Dictionaries" directory as needed, or used from the <cache_path> directory if the file already exists there. The dictionary file will be downloaded from http://cache.pack.google.com/edgedl/chrome/dict/<LANG>-3-0.bdic where <LANG> is the language abbreviation.
- On OS X the spell checking implementation will use the system NSSpellChecker implementation.

The following command-line flags have been added:
--disable-spell-checking => Disable spell-checking support (no red underline, no dictionary file download, etc).
--enable-spelling-auto-correct => Automatically correct common misspellings while typing (like 'omre' to 'more' on Windows/Linux or 'ehlo' to 'helo' on OS X).
--enable-spelling-service => Enable use of the remote Google spelling service (this requires Google API keys).
--override-spell-check-lang=<LANG> => Use the specified dictionary language <LANG> instead of the language specified in the locales.pak file. To see the default/supported dictionary languages: https://code.google.com/p/chromium/codesearch#search/&q=IDS_SPELLCHECK_DICTIONARY%20xtb&sq=package:chromium


git-svn-id: https://chromiumembedded.googlecode.com/svn/trunk@1859 5089003a-bbd8-11dd-ad1f-f1f9622dbc98

libcef/browser/browser_context_impl.cc

@@ -15,6 +15,7 @@
 #include "base/bind.h"
 #include "base/logging.h"
 #include "base/threading/thread.h"
+#include "components/keyed_service/content/browser_context_dependency_manager.h"
 #include "content/public/browser/download_manager.h"
 #include "content/public/browser/browser_thread.h"
 #include "content/public/browser/resource_context.h"
@@ -61,6 +62,10 @@ CefBrowserContextImpl::~CefBrowserContextImpl() {
     BrowserThread::DeleteSoon(
         BrowserThread::IO, FROM_HERE, resource_context_.release());
   }
+
+  // Remove any BrowserContextKeyedServiceFactory associations.
+  BrowserContextDependencyManager::GetInstance()->DestroyBrowserContextServices(
+      this);
 }
 
 base::FilePath CefBrowserContextImpl::GetPath() const {