Fix Metal includes breaking macOS local builds

Before this fix, skia (and thus Chrome) would fail to compile on macOS when the user (developer) had a case-sensitive file-system.

So I've replaced the incorrect includes of <metal/metal.h> by <Metal/Metal.h>

Change-Id: I6ebcc0f46608f6d840d80d18e5f5baf0744a7f16
Reviewed-on: https://skia-review.googlesource.com/c/skia/+/225776
Reviewed-by: Jim Van Verth <jvanverth@google.com>
Commit-Queue: Mike Klein <mtklein@google.com>
diff --git a/AUTHORS b/AUTHORS
index 192d69c..80776a6 100644
--- a/AUTHORS
+++ b/AUTHORS
@@ -11,6 +11,7 @@
 #
 # Please keep the list sorted alphabetically.
 
+Aaron O'Mullan <aaron.omullan@gmail.com>
 ACCESS CO., LTD. <*@access-company.com>
 Amazon, Inc <*@amazon.com>
 Anthony Catel <paraboul@gmail.com>
diff --git a/src/gpu/mtl/GrMtlBuffer.h b/src/gpu/mtl/GrMtlBuffer.h
index e409650..1376823 100644
--- a/src/gpu/mtl/GrMtlBuffer.h
+++ b/src/gpu/mtl/GrMtlBuffer.h
@@ -11,7 +11,7 @@
 #include "src/gpu/GrGpuBuffer.h"
 #include "src/gpu/mtl/GrMtlUniformHandler.h"
 
-#import <metal/metal.h>
+#import <Metal/Metal.h>
 
 class GrMtlCaps;
 class GrMtlGpu;
diff --git a/src/gpu/mtl/GrMtlDepthStencil.h b/src/gpu/mtl/GrMtlDepthStencil.h
index 8efeb37..0f61af8 100644
--- a/src/gpu/mtl/GrMtlDepthStencil.h
+++ b/src/gpu/mtl/GrMtlDepthStencil.h
@@ -8,7 +8,7 @@
 #ifndef GrMtlDepthStencil_DEFINED
 #define GrMtlDepthStencil_DEFINED
 
-#import <metal/metal.h>
+#import <Metal/Metal.h>
 
 #include "include/gpu/GrTypes.h"
 #include "src/core/SkOpts.h"
diff --git a/src/gpu/mtl/GrMtlGpuCommandBuffer.h b/src/gpu/mtl/GrMtlGpuCommandBuffer.h
index 7e820e3..3bf1af5 100644
--- a/src/gpu/mtl/GrMtlGpuCommandBuffer.h
+++ b/src/gpu/mtl/GrMtlGpuCommandBuffer.h
@@ -13,7 +13,7 @@
 #include "src/gpu/GrOpFlushState.h"
 #include "src/gpu/mtl/GrMtlGpu.h"
 
-#import <metal/metal.h>
+#import <Metal/Metal.h>
 
 typedef uint32_t GrColor;
 class GrMtlBuffer;
diff --git a/src/gpu/mtl/GrMtlPipelineState.h b/src/gpu/mtl/GrMtlPipelineState.h
index 6e39f15..821fbd3 100644
--- a/src/gpu/mtl/GrMtlPipelineState.h
+++ b/src/gpu/mtl/GrMtlPipelineState.h
@@ -14,7 +14,7 @@
 #include "src/gpu/mtl/GrMtlBuffer.h"
 #include "src/gpu/mtl/GrMtlPipelineStateDataManager.h"
 
-#import <metal/metal.h>
+#import <Metal/Metal.h>
 
 class GrMtlGpu;
 class GrMtlPipelineStateDataManager;
diff --git a/src/gpu/mtl/GrMtlPipelineStateBuilder.h b/src/gpu/mtl/GrMtlPipelineStateBuilder.h
index ed078ff..8242702 100644
--- a/src/gpu/mtl/GrMtlPipelineStateBuilder.h
+++ b/src/gpu/mtl/GrMtlPipelineStateBuilder.h
@@ -15,7 +15,7 @@
 #include "src/gpu/mtl/GrMtlVaryingHandler.h"
 #include "src/sksl/SkSLCompiler.h"
 
-#import <metal/metal.h>
+#import <Metal/Metal.h>
 
 class GrMtlGpu;
 class GrMtlPipelineState;
diff --git a/src/gpu/mtl/GrMtlResourceProvider.h b/src/gpu/mtl/GrMtlResourceProvider.h
index 9095080..d7e1910 100644
--- a/src/gpu/mtl/GrMtlResourceProvider.h
+++ b/src/gpu/mtl/GrMtlResourceProvider.h
@@ -15,7 +15,7 @@
 #include "src/gpu/mtl/GrMtlPipelineStateBuilder.h"
 #include "src/gpu/mtl/GrMtlSampler.h"
 
-#import <metal/metal.h>
+#import <Metal/Metal.h>
 
 class GrMtlGpu;
 class GrMtlCommandBuffer;
diff --git a/src/gpu/mtl/GrMtlSampler.h b/src/gpu/mtl/GrMtlSampler.h
index bd3c0a3..f0e21dd 100644
--- a/src/gpu/mtl/GrMtlSampler.h
+++ b/src/gpu/mtl/GrMtlSampler.h
@@ -8,7 +8,7 @@
 #ifndef GrMtlSampler_DEFINED
 #define GrMtlSampler_DEFINED
 
-#import <metal/metal.h>
+#import <Metal/Metal.h>
 
 #include "src/core/SkOpts.h"
 #include <atomic>
diff --git a/tests/MtlBackendAllocationTest.mm b/tests/MtlBackendAllocationTest.mm
index 3a8673f..5fcf050 100644
--- a/tests/MtlBackendAllocationTest.mm
+++ b/tests/MtlBackendAllocationTest.mm
@@ -9,7 +9,7 @@
 #include "src/gpu/GrContextPriv.h"
 #include "tests/Test.h"
 
-#import <metal/metal.h>
+#import <Metal/Metal.h>
 #include "src/gpu/mtl/GrMtlCaps.h"
 
 // In BackendAllocationTest.cpp