First pass at font cache refactor: Create an atlas manager per texture

include/gpu/GrTypes.h

Index: include/gpu/GrTypes.h
diff --git a/include/gpu/GrTypes.h b/include/gpu/GrTypes.h
index 2405679c0f8007b0c450d607d86d0aa9d39e4312..b78976361b4dfdd76d550ab270357ffdf39c5fba 100644
--- a/include/gpu/GrTypes.h
+++ b/include/gpu/GrTypes.h
@@ -248,9 +248,10 @@ enum GrMaskFormat {
     kA8_GrMaskFormat,    //!< 1-byte per pixel
     kA565_GrMaskFormat,  //!< 2-bytes per pixel
     kA888_GrMaskFormat,  //!< 4-bytes per pixel
-
-    kCount_GrMaskFormats //!< used to allocate arrays sized for mask formats
+    
+    kLast_GrMaskFormat = kA888_GrMaskFormat
 };
+static const int kMaskFormatCount = kLast_GrMaskFormat + 1;
 
 /**
  *  Return the number of bytes-per-pixel for the specified mask format.