gpu/BUILD.gn: use the more detail dawn targets.

libdawn is deprecated and was split in libdawn_proc and dawncpp so each
could be used separately. Make Chromium use the split targets so the
temporary libdawn group used for backwards compatibility can be removed.

BUG=dawn:22

Change-Id: I2db79b5b14c12b10111bd03bf66ca2692c07c200
Reviewed-on: https://chromium-review.googlesource.com/c/chromium/src/+/1869209Reviewed-by: Kenneth Russell <kbr@chromium.org>
Commit-Queue: Corentin Wallez <cwallez@chromium.org>
Cr-Commit-Position: refs/heads/master@{#707937}

gpu/BUILD.gn

@@ -393,10 +393,6 @@ test("gl_tests") {
     deps += [ "//ui/ozone" ]
   }
 
-  if (use_dawn) {
-    deps += [ "//third_party/dawn/src/dawn:libdawn" ]
-  }
-
   libs = []
 
   if (is_android) {
@@ -419,7 +415,8 @@ test("gl_tests") {
   if (use_dawn) {
     deps += [
       "//third_party/dawn:libdawn_native",
-      "//third_party/dawn/src/dawn:libdawn",
+      "//third_party/dawn/src/dawn:libdawn_proc",
+      "//third_party/dawn/src/dawn:dawncpp",
     ]
   }
 }