Split a portion of BufferedResourceLoader into a separate class ActiveLoader.

tools/heapcheck/suppressions.txt

 # There are three kinds of suppressions in this file.
 # 1. third party stuff we have no control over
 #
 # 2. intentional unit test errors, or stuff that is somehow a false positive
 # in our own code, or stuff that is so trivial it's not worth fixing
 #
 # 3. Suppressions for real chromium bugs that are not yet fixed.
 # These should all be in chromium's bug tracking system (but a few aren't yet).
 # Periodically we should sweep this file and the bug tracker clean by
 # running overnight and removing outdated bugs/suppressions.
@@ skipping 1753 matching lines @@
 }
 {
    bug_105667_b
    Heapcheck:Leak
    fun:browser_sync::TypedUrlDataTypeController::StopAssociationAsync
    fun:browser_sync::NonFrontendDataTypeController::Stop
    fun:browser_sync::DataTypeManagerImpl::FinishStop
    fun:browser_sync::DataTypeManagerImpl::Stop
    fun:ProfileSyncService::Shutdown
 }
-{
-   bug_100914_a
-   Heapcheck:Leak
-   ...
-   fun:webkit_media::MockBufferedDataSource::CreateMockResourceLoader
-}
-{
-   bug_100914_b
-   Heapcheck:Leak
-   ...
-   fun:BufferedDataSourceTest
-}
-{
-   bug_100914_c
-   Heapcheck:Leak
-   ...
-   fun:webkit_media::BufferedDataSourceTest::Initialize
-}
-{
-   bug_100914_d
-   Heapcheck:Leak
-   fun:webkit_media::MockBufferedDataSource::MockBufferedDataSource
-   fun:webkit_media::BufferedDataSourceTest::BufferedDataSourceTest
-}