Add support for ManagedMemoryPolicy (de)serialization

cc/proto/memory_allocation.proto

Index: cc/proto/memory_allocation.proto
diff --git a/cc/proto/skregion.proto b/cc/proto/memory_allocation.proto
similarity index 58%
copy from cc/proto/skregion.proto
copy to cc/proto/memory_allocation.proto
index 1f6b337e9b39c5e926b1ff497263b46687c0b760..436461d6044e3df3a74f811ff06363ea7c321cba 100644
--- a/cc/proto/skregion.proto
+++ b/cc/proto/memory_allocation.proto
@@ -4,17 +4,16 @@
 
 syntax = "proto2";
 
-option optimize_for = LITE_RUNTIME;
-
 package cc.proto;
 
-message SkRegion {
-  enum Op {
-    Op_Difference = 0;
-    Op_Intersect = 1;
-    Op_Union = 2;
-    Op_XOR = 3;
-    Op_ReverseDifference = 4;
-    Op_Replace = 5;
+option optimize_for = LITE_RUNTIME;
+
+message MemoryAllocation {
+  enum PriorityCutoff {
+    UNKNOWN = 0;
+    ALLOW_NOTHING = 1;
+    ALLOW_REQUIRED_ONLY = 2;
+    ALLOW_NICE_TO_HAVE = 3;
+    ALLOW_EVERYTHING = 4;
   }
-}
+}