BUILD.gn: enable additional warnings.

Skia uses more warnings than Dawn, enable in Dawn directly so that
rolls of Dawn into Skia don't introduce warnings. These warnings
seem useful anyway.

Bug: chromium:1064305

Change-Id: I13dc776af84151131584a95caeee2cd21ae80fea
Reviewed-on: https://dawn-review.googlesource.com/c/dawn/+/18964
Commit-Queue: Corentin Wallez <cwallez@chromium.org>
Reviewed-by: Austin Eng <enga@chromium.org>

src/common/BUILD.gn

@@ -86,6 +86,17 @@ config("dawn_internal") {
   # Only internal Dawn targets can use this config, this means only targets in
   # this BUILD.gn file.
   visibility = [ ":*" ]
+
+  # Enable more warnings that were found when using Dawn in other projects
+  if (is_clang) {
+    cflags = [
+      "-Wstrict-prototypes",
+      "-Winconsistent-missing-destructor-override",
+      "-Wshadow-field",
+      "-Wmissing-field-initializers",
+      "-Wcstring-format-directive",
+    ]
+  }
 }
 
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