Revert "Move include into head to fix build breakage."

This reverts commit fac695317f.

Reason for revert: needed to revert early change

Original change's description:
> Move include into head to fix build breakage.
> 
> Bug: skia:
> Change-Id: I47e182bf18f56c9c0749a1fd79b85d26fce9887e
> Reviewed-on: https://skia-review.googlesource.com/131022
> Commit-Queue: Greg Daniel <egdaniel@google.com>
> Commit-Queue: Brian Osman <brianosman@google.com>
> Auto-Submit: Greg Daniel <egdaniel@google.com>
> Reviewed-by: Brian Osman <brianosman@google.com>

TBR=egdaniel@google.com,rmistry@google.com,brianosman@google.com

Change-Id: Ie396d213c2e43e053a6c6df9cfb18ac4be8b909c
No-Presubmit: true
No-Tree-Checks: true
No-Try: true
Bug: skia:
Reviewed-on: https://skia-review.googlesource.com/131080
Reviewed-by: Greg Daniel <egdaniel@google.com>
Commit-Queue: Greg Daniel <egdaniel@google.com>

include/gpu/vk/GrVkBackendContext.h

@@ -12,7 +12,8 @@
 
 #include "vk/GrVkDefines.h"
 #include "vk/GrVkInterface.h"
-#include "vk/GrVkMemoryAllocator.h"
+
+class GrVkMemoryAllocator;
 
 enum GrVkExtensionFlags {
     kEXT_debug_report_GrVkExtensionFlag    = 0x0001,

src/gpu/vk/GrVkBackendContext.cpp

@@ -8,6 +8,7 @@
 #include "SkAutoMalloc.h"
 #include "vk/GrVkBackendContext.h"
 #include "vk/GrVkExtensions.h"
+#include "vk/GrVkMemoryAllocator.h"
 #include "vk/GrVkUtil.h"
 
 ////////////////////////////////////////////////////////////////////////////////