Make FencedAlloctor fail on size = 0.

gpu/command_buffer/client/mapped_memory_unittest.cc

Index: gpu/command_buffer/client/mapped_memory_unittest.cc
diff --git a/gpu/command_buffer/client/mapped_memory_unittest.cc b/gpu/command_buffer/client/mapped_memory_unittest.cc
index 964d7634047a652e05d77b7f25013352e23481b9..ab94ef0fa4f5f98b7cd69a80095796b8c1f34972 100644
--- a/gpu/command_buffer/client/mapped_memory_unittest.cc
+++ b/gpu/command_buffer/client/mapped_memory_unittest.cc
@@ -205,6 +205,25 @@ TEST_F(MappedMemoryManagerTest, Basic) {
   manager_->Free(mem5);
 }
 
+TEST_F(MappedMemoryManagerTest, AllocZero) {
+  int32 id = -1;
+  unsigned int offset = 0xFFFFFFFFU;
+  void* mem = manager_->Alloc(0, &id, &offset);
+  ASSERT_TRUE(mem);
+  EXPECT_NE(-1, id);
+  EXPECT_EQ(0u, offset);
+  manager_->Free(mem);
+
+  id = -1;
+  offset = 0xFFFFFFFFU;
+  mem = manager_->Alloc(0, &id, &offset);
+
+  int32 token = helper_.get()->InsertToken();
+  manager_->FreePendingToken(mem, token);
+  EXPECT_GT(token, GetToken());
+  helper_->Finish();
+}
+
 TEST_F(MappedMemoryManagerTest, FreePendingToken) {
   const unsigned int kSize = 128;
   const unsigned int kAllocCount = (kBufferSize / kSize) * 2;