Issue #80- De-unify gfx/layers

Excludes layers/ipc/CompositorBridgeParent and CrossProcessCompositorBridgeParent
because the latter purposely uses functions implemented in the former.
See also code comment in CrossProcessCompositorBridgeParent.cpp

Note: likely dead code for us anyway; likely not worth investing in to solve.

gfx/layers/ipc/CrossProcessCompositorBridgeParent.cpp

@@ -84,9 +84,10 @@
 #include "LayerScope.h"
 
 namespace mozilla {
-
 namespace layers {
 
+using namespace std;
+
 // defined in CompositorBridgeParent.cpp
 typedef map<uint64_t, CompositorBridgeParent::LayerTreeState> LayerTreeMap;
 extern LayerTreeMap sIndirectLayerTrees;