Remove ReadLockHandle and ReadLockInit code (bug 1445008, r=aosmond)

This code is unused now that ReadLockDescriptors are not sent in layer transactions.

gfx/layers/wr/WebRenderLayerManager.cpp

@@ -211,8 +211,6 @@ WebRenderLayerManager::EndEmptyTransaction(EndTransactionFlags aFlags)
 
   mWebRenderCommandBuilder.EmptyTransaction();
 
-  WrBridge()->ClearReadLocks();
-
   mLatestTransactionId = mTransactionIdAllocator->GetTransactionId(/*aThrottle*/ true);
   TimeStamp transactionStart = mTransactionIdAllocator->GetTransactionStart();
 
@@ -283,8 +281,6 @@ WebRenderLayerManager::EndTransactionWithoutLayer(nsDisplayList* aDisplayList,
   mWidget->AddWindowOverlayWebRenderCommands(WrBridge(), builder, resourceUpdates);
   mWindowOverlayChanged = false;
 
-  WrBridge()->ClearReadLocks();
-
   if (AsyncPanZoomEnabled()) {
     mScrollData.SetFocusTarget(mFocusTarget);
     mFocusTarget = FocusTarget();