GCC: Define MemoryAllocInfoMapKey's hash before using in unordered_map

GCC complains that std::hash specialization for
MemoryAllocInfoMapKey type should be positioned before it is
used in std::unordered_map.

Bug: chromium:40565911
Change-Id: Ia3dd2a699431720b030839d94ea796894ba8b822
Reviewed-on: https://chromium-review.googlesource.com/c/angle/angle/+/5642294
Auto-Submit: DongHwan Yu <[email protected]>
Commit-Queue: Shahbaz Youssefi <[email protected]>
Reviewed-by: Shahbaz Youssefi <[email protected]>

src/libANGLE/renderer/vulkan/MemoryTracking.h

@@ -122,6 +122,20 @@ class MemoryReport final : angle::NonCopyable
  angle::HashMap<uint64_t, int> mUniqueIDCounts;
 };
 } // namespace vk
+} // namespace rx
+
+// Introduce std::hash for MemoryAllocInfoMapKey.
+namespace std
+{
+template <>
+struct hash<rx::vk::MemoryAllocInfoMapKey>
+{
+ size_t operator()(const rx::vk::MemoryAllocInfoMapKey &key) const { return key.hash(); }
+};
+} // namespace std
+
+namespace rx
+{
 
 // Memory tracker for allocations and deallocations, which is used in vk::Renderer.
 class MemoryAllocationTracker : angle::NonCopyable
@@ -208,14 +222,4 @@ class MemoryAllocationTracker : angle::NonCopyable
 };
 } // namespace rx
 
-// Introduce std::hash for MemoryAllocInfoMapKey.
-namespace std
-{
-template <>
-struct hash<rx::vk::MemoryAllocInfoMapKey>
-{
- size_t operator()(const rx::vk::MemoryAllocInfoMapKey &key) const { return key.hash(); }
-};
-} // namespace std
-
 #endif // LIBANGLE_RENDERER_VULKAN_MEMORYTRACKING_H_