fileSystem() for the blink::Platform used in blink unit tests.

content/test/test_webkit_platform_support.cc

Index: content/test/test_webkit_platform_support.cc
diff --git a/content/test/test_webkit_platform_support.cc b/content/test/test_webkit_platform_support.cc
index c0e3673a6d3e26b11b58e74c6620e731bef23373..a69fe64f3263a41d7ae894734478fce86cf6200f 100644
--- a/content/test/test_webkit_platform_support.cc
+++ b/content/test/test_webkit_platform_support.cc
@@ -11,6 +11,7 @@
 #include "base/metrics/stats_counters.h"
 #include "base/path_service.h"
 #include "base/strings/utf_string_conversions.h"
+#include "content/child/fileapi/webfilesystem_impl.h"
 #include "content/public/common/content_switches.h"
 #include "content/test/mock_webclipboard_impl.h"
 #include "content/test/web_gesture_curve_mock.h"
@@ -127,6 +128,11 @@ blink::WebFileUtilities* TestWebKitPlatformSupport::fileUtilities() {
   return &file_utilities_;
 }
 
+blink::WebFileSystem* TestWebKitPlatformSupport::fileSystem() {
+  return WebFileSystemImpl::ThreadSpecificInstance(
+      base::MessageLoopProxy::current());
+}
+
 blink::WebIDBFactory* TestWebKitPlatformSupport::idbFactory() {
   NOTREACHED() <<
       "IndexedDB cannot be tested with in-process harnesses.";