Delay creation of cpu-side buffer memory until actually needed

src/gpu/GrBufferAllocPool.cpp

Index: src/gpu/GrBufferAllocPool.cpp
diff --git a/src/gpu/GrBufferAllocPool.cpp b/src/gpu/GrBufferAllocPool.cpp
index bb73a101eec20837758234f3f97ad1bc36696468..e3f30b0c1c57bce3e8f66501ee6559cb3fe36985 100644
--- a/src/gpu/GrBufferAllocPool.cpp
+++ b/src/gpu/GrBufferAllocPool.cpp
@@ -78,10 +78,7 @@ void GrBufferAllocPool::reset() {
     VALIDATE();
     fBytesInUse = 0;
     this->deleteBlocks();
-
-    // we may have created a large cpu mirror of a large VB. Reset the size to match our minimum.
-    this->resetCpuData(fMinBlockSize);
-
+    this->resetCpuData(0);      // delete all the cpu-side memory
     VALIDATE();
 }