Enable "gn check" for //third_party/blink/renderer/platform

- Add missing dependencies
- Remove non-existent synchronous_compositor_registry.h

This CL has no behavior changes.

Bug: 800764
Change-Id: Iabd809cef86acfd072895a951355146ff9207773
Reviewed-on: https://chromium-review.googlesource.com/c/chromium/src/+/2409418
Commit-Queue: Takuto Ikuta <tikuta@chromium.org>
Auto-Submit: Kent Tamura <tkent@chromium.org>
Reviewed-by: Takuto Ikuta <tikuta@chromium.org>
Cr-Commit-Position: refs/heads/master@{#806857}

.gn

@@ -253,7 +253,6 @@ no_check_targets = [
   "//third_party/blink/renderer/modules/canvas:*",  # 1 error
   "//third_party/blink/renderer/modules/font_access:*",  # 3 errors
   "//third_party/blink/renderer/modules/peerconnection:*",  # 43 errors
-  "//third_party/blink/renderer/platform:*",  # 10 errors
 
   "//third_party/breakpad:*",  # 34 errors
   "//third_party/ced/*",

third_party/blink/renderer/platform/BUILD.gn

@@ -1547,7 +1547,6 @@ component("platform") {
     sources += [
       "widget/input/synchronous_compositor_proxy.cc",
       "widget/input/synchronous_compositor_proxy.h",
-      "widget/input/synchronous_compositor_registry.h",
     ]
   }
 
@@ -1597,6 +1596,8 @@ component("platform") {
     "//crypto",
     "//device/vr/public/mojom:mojom_blink",
     "//gin",
+    "//gpu:gpu",
+    "//gpu/command_buffer/client:webgpu_interface",
     "//jingle:webrtc_glue",
     "//media",
     "//media/capture:capture_switches",
@@ -1818,6 +1819,7 @@ static_library("test_support") {
     "//cc",
     "//cc:test_support",
     "//components/viz/test:test_support",
+    "//gpu:raster",
     "//testing/gmock",
     "//testing/gtest:gtest",
     "//testing/perf",
@@ -2271,9 +2273,9 @@ source_set("blink_fuzzer_test_support") {
     "testing/blink_fuzzer_test_support.cc",
     "testing/blink_fuzzer_test_support.h",
   ]
+  public_deps = [ ":test_support" ]
   deps = [
     ":platform",
-    ":test_support",
     "//base/test:test_config",
     "//content/test:test_support",
   ]