Dynamically allocate the GrDrawContexts

This CL moves the allocation and storage of the GrTextContexts into the DrawingManager. The GrDrawContexts now just get their GrTextContext from the DrawingManager.

Review URL: https://codereview.chromium.org/1375153007
diff --git a/src/gpu/GrTextContext.cpp b/src/gpu/GrTextContext.cpp
index 1041b88..a2e245d 100644
--- a/src/gpu/GrTextContext.cpp
+++ b/src/gpu/GrTextContext.cpp
@@ -27,7 +27,9 @@
     , fSurfaceProps(surfaceProps) {
 }
 
-GrTextContext::~GrTextContext() { delete fFallbackTextContext; }
+GrTextContext::~GrTextContext() {
+    delete fFallbackTextContext;
+}
 
 void GrTextContext::drawText(GrDrawContext* dc, GrRenderTarget* rt,
                              const GrClip& clip, const GrPaint& paint,