Explicitly suppress -Wimplicit-fallthrough for angle and its deps.

No behavior change since that warning isn't enabled anywhere yet, and
it's opt-in.  This is a prerequisite for
https://chromium-review.googlesource.com/c/chromium/src/+/895726

Bug: chromium:177475

Change-Id: Ie5ffccd240a65646fe07e7d4475f63c4e8620746
Reviewed-on: https://chromium-review.googlesource.com/895728
Reviewed-by: Jamie Madill <jmadill@chromium.org>
Commit-Queue: Nico Weber <thakis@chromium.org>

BUILD.gn

@@ -96,8 +96,13 @@ config("extra_warnings") {
     ]
   }
   if (is_clang) {
-    # Remove when crbug.com/428099 is resolved.
-    cflags += [ "-Winconsistent-missing-override" ]
+    cflags += [
+      # Remove when crbug.com/428099 is resolved.
+      "-Winconsistent-missing-override",
+
+      # TODO(thakis): Consider enabling this, https://crbug.com/807632
+      "-Wno-implicit-fallthrough",
+    ]
   }
 }
 

src/vulkan_support/BUILD.gn

@@ -241,9 +241,14 @@ config("vulkan_internal_config") {
   if (is_clang || !is_win) {
     cflags = [ "-Wno-unused-function" ]
 
-    # See https://github.com/KhronosGroup/Vulkan-LoaderAndValidationLayers/issues/1649
-    # TODO(jmadill): Lift this once github issue is fixed.
-    cflags += [ "-Wno-ignored-attributes" ]
+    cflags += [
+      # See https://github.com/KhronosGroup/Vulkan-LoaderAndValidationLayers/issues/1649
+      # TODO(jmadill): Lift this once github issue is fixed.
+      "-Wno-ignored-attributes",
+
+      # TODO(thakis): Consider enabling this, https://crbug.com/807632
+      "-Wno-implicit-fallthrough",
+    ]
   }
   if (is_linux) {
     defines += [
@@ -475,6 +480,12 @@ config("spirv_tools_config") {
     ]
   }
 }
+config("spirv_tools_internal_config") {
+  if (is_clang) {
+    # TODO(thakis): Consider enabling this, https://crbug.com/807632
+    cflags = [ "-Wno-implicit-fallthrough" ]
+  }
+}
 
 static_library("spirv_tools") {
   deps = [
@@ -565,6 +576,7 @@ static_library("spirv_tools") {
     "$spirv_tools_dir/source/validate_type_unique.cpp",
   ]
   public_configs = [ ":spirv_tools_config" ]
+  configs += [ ":spirv_tools_internal_config" ]
 
   foreach(target_name, spvtools_vendor_tables) {
     deps += [ ":$target_name" ]
@@ -588,6 +600,10 @@ config("glslang_internal_config") {
       "-Wno-reorder",
     ]
   }
+  if (is_clang) {
+    # TODO(thakis): Consider enabling this, https://crbug.com/807632
+    cflags += [ "-Wno-implicit-fallthrough" ]
+  }
 }
 
 static_library("glslang") {