Revert "Skia/Metal raster: Add viz::MetalContextProvider"

This reverts commit 45f012f.

Reason for revert: Broke mac compile

Original change's description:
> Skia/Metal raster: Add viz::MetalContextProvider
> 
> Add viz::MetalContextProvider, and add Metal to the Skia build by
> default. Do not wire up any of this yet.
> 
> Bug: 952063
> Change-Id: I897d052bdbf046114c1ddc0527c1d3cafc8777c5
> Reviewed-on: https://chromium-review.googlesource.com/c/chromium/src/+/1577296
> Reviewed-by: Brian Osman <brianosman@google.com>
> Reviewed-by: Eric Karl <ericrk@chromium.org>
> Commit-Queue: ccameron <ccameron@chromium.org>
> Cr-Commit-Position: refs/heads/master@{#652899}

TBR=ccameron@chromium.org,brianosman@google.com,ericrk@chromium.org

Change-Id: Ic0a4f5201df55ac7ef0b8a191b572a9bbeee6dc0
No-Presubmit: true
No-Tree-Checks: true
No-Try: true
Bug: 952063
Reviewed-on: https://chromium-review.googlesource.com/c/chromium/src/+/1577783
Reviewed-by: ccameron <ccameron@chromium.org>
Commit-Queue: ccameron <ccameron@chromium.org>
Cr-Commit-Position: refs/heads/master@{#652909}

components/viz/common/BUILD.gn

@@ -40,34 +40,6 @@ viz_component("resource_format_utils") {
   ]
 }
 
-if (is_mac) {
-  viz_component("metal_context_provider") {
-    output_name = "viz_metal_context_provider"
-
-    defines = [ "VIZ_METAL_CONTEXT_PROVIDER_IMPLEMENTATION" ]
-
-    sources = [
-      "gpu/metal_context_provider.h",
-      "gpu/metal_context_provider.mm",
-      "viz_metal_context_provider_export.h",
-    ]
-
-    public_deps = [
-      "//skia",
-    ]
-
-    deps = [
-      "//base",
-      "//ui/gfx",
-    ]
-
-    libs = [
-      "Metal.framework",
-      "Foundation.framework",
-    ]
-  }
-}
-
 if (enable_vulkan) {
   viz_component("vulkan_context_provider") {
     output_name = "viz_vulkan_context_provider"
@@ -284,9 +256,6 @@ viz_component("common") {
   if (enable_vulkan) {
     public_deps += [ ":vulkan_context_provider" ]
   }
-  if (is_mac) {
-    public_deps += [ ":metal_context_provider" ]
-  }
 }
 
 viz_source_set("unit_tests") {

skia/BUILD.gn

@@ -25,6 +25,7 @@ skia_support_skottie = true
 
 declare_args() {
   skia_whitelist_serialized_typefaces = false
+  skia_use_metal = false
 }
 
 # External-facing config for dependent code.
@@ -101,10 +102,7 @@ config("skia_config") {
   }
 
   if (is_mac) {
-    defines += [
-      "SK_BUILD_FOR_MAC",
-      "SK_METAL",
-    ]
+    defines += [ "SK_BUILD_FOR_MAC" ]
   }
 
   if (is_win) {
@@ -558,14 +556,20 @@ component("skia") {
   }
 
   if (is_mac) {
-    deps += [ ":skia_metal" ]
-    defines += [ "SK_METAL" ]
+    if (skia_use_metal) {
+      deps += [ ":skia_metal" ]
+      defines += [ "SK_METAL" ]
+      libs += [
+        "Metal.framework",
+        "Foundation.framework",
+      ]
+    }
+
     libs = [
       "AppKit.framework",
       "CoreFoundation.framework",
       "CoreGraphics.framework",
       "CoreText.framework",
-      "Metal.framework",
       "Foundation.framework",
     ]
   }
@@ -797,7 +801,7 @@ skia_source_set("skia_opts") {
 }
 
 # Split out metal sources, because they require ARC.
-if (is_mac) {
+if (is_mac && skia_use_metal) {
   skia_source_set("skia_metal") {
     defines = [ "SK_METAL" ]
     sources = skia_metal_sources