Linux warning fixes

Review URL: https://codereview.appspot.com/6500045/



git-svn-id: http://skia.googlecode.com/svn/trunk@5337 2bbb7eff-a529-9590-31e7-b0007b416f81
diff --git a/src/gpu/GrMemoryPool.cpp b/src/gpu/GrMemoryPool.cpp
index 01f303f..17d70ab 100644
--- a/src/gpu/GrMemoryPool.cpp
+++ b/src/gpu/GrMemoryPool.cpp
@@ -110,7 +110,7 @@
     block->fLiveCount = 0;
     block->fFreeSize = size;
     block->fCurrPtr = reinterpret_cast<intptr_t>(block) + kHeaderSize;
-    block->fPrevPtr = NULL;
+    block->fPrevPtr = 0; // gcc warns on assigning NULL to an intptr_t.
     return block;
 }