Add PERSISTENT_MAP usage for GpuMemoryBuffers.

content/common/gpu/client/gpu_memory_buffer_impl_shared_memory.cc

Index: content/common/gpu/client/gpu_memory_buffer_impl_shared_memory.cc
diff --git a/content/common/gpu/client/gpu_memory_buffer_impl_shared_memory.cc b/content/common/gpu/client/gpu_memory_buffer_impl_shared_memory.cc
index cf9505625ffd53ae1b42a63b7909f525dde594f1..992372b78066484004a83318ae90f6f6e1936c26 100644
--- a/content/common/gpu/client/gpu_memory_buffer_impl_shared_memory.cc
+++ b/content/common/gpu/client/gpu_memory_buffer_impl_shared_memory.cc
@@ -121,6 +121,19 @@ bool GpuMemoryBufferImplSharedMemory::IsFormatSupported(Format format) {
 }
 
 // static
+bool GpuMemoryBufferImplSharedMemory::IsUsageSupported(Usage usage) {
+  switch (usage) {
+    case MAP:
+    case PERSISTENT_MAP:
+      return true;
+    case SCANOUT:
+      return false;
+  }
+  NOTREACHED();
+  return false;
+}
+
+// static
 bool GpuMemoryBufferImplSharedMemory::IsSizeValidForFormat(
     const gfx::Size& size,
     Format format) {