Add GrResourceAllocator class + unit test

Change-Id: I2700e8cb4213479b680519ba67f078cc3fb71376
Reviewed-on: https://skia-review.googlesource.com/23661
Reviewed-by: Brian Salomon <bsalomon@google.com>
Commit-Queue: Robert Phillips <robertphillips@google.com>
diff --git a/gn/gpu.gni b/gn/gpu.gni
index 06f9908..4188131 100644
--- a/gn/gpu.gni
+++ b/gn/gpu.gni
@@ -161,6 +161,8 @@
   "$_src/gpu/GrPathRenderingRenderTargetContext.h",
   "$_src/gpu/GrRenderTargetOpList.cpp",
   "$_src/gpu/GrRenderTargetOpList.h",
+  "$_src/gpu/GrResourceAllocator.cpp",
+  "$_src/gpu/GrResourceAllocator.h",
   "$_src/gpu/GrResourceCache.cpp",
   "$_src/gpu/GrResourceCache.h",
   "$_src/gpu/GrResourceHandle.h",