Move GrAtlasTextContext to GrDrawingManager, so we only have one.

include/gpu/GrDrawContext.h

Index: include/gpu/GrDrawContext.h
diff --git a/include/gpu/GrDrawContext.h b/include/gpu/GrDrawContext.h
index def541d9a9814c0aeaa72ec897fa74f243edc96c..6e98404a44bd6751c2ef03281e96ccbf1ee0e498 100644
--- a/include/gpu/GrDrawContext.h
+++ b/include/gpu/GrDrawContext.h
@@ -17,7 +17,6 @@
 #include "../private/GrInstancedPipelineInfo.h"
 #include "../private/GrSingleOwner.h"
 
-class GrAtlasTextContext;
 class GrAuditTrail;
 class GrClip;
 class GrContext;
@@ -367,7 +366,6 @@ private:
     // In MDB-mode the drawTarget can be closed by some other drawContext that has picked
     // it up. For this reason, the drawTarget should only ever be accessed via 'getDrawTarget'.
     GrDrawTarget*                     fDrawTarget;
-    SkAutoTDelete<GrAtlasTextContext> fAtlasTextContext;
     GrContext*                        fContext;
     GrInstancedPipelineInfo           fInstancedPipelineInfo;