Revert "Roll clang 318667:321204."

This reverts commit ece1b14db2dedf6a9a4086b46e8cc6c2acd1b62d.

Reason for revert: suspected of causing the crash in crbug/797267

Original change's description:
> Roll clang 318667:321204.
>
> Ran `tools/clang/scripts/upload_revision.py 321204`
> and cherry-picked the non-clang changes from
> https://chromium-review.googlesource.com/c/chromium/src/+/828400 .
>
> TBR=brettw@chromium.org,rsesek@chromium.org,hans@chromium.org
>
> Bug: 787920
> Cq-Include-Trybots: master.tryserver.chromium.android:android_arm64_dbg_recipe;master.tryserver.chromium.android:android_compile_mips_dbg;master.tryserver.chromium.android:android_compile_x64_dbg;master.tryserver.chromium.android:android_compile_x86_dbg
> Change-Id: Iaec5677e2afee0edb685db816e00f3c900214d14
> Reviewed-on: https://chromium-review.googlesource.com/835358
> Commit-Queue: Peter Collingbourne <pcc@chromium.org>
> Reviewed-by: Robert Sesek <rsesek@chromium.org>
> Reviewed-by: Hans Wennborg <hans@chromium.org>
> Reviewed-by: Peter Collingbourne <pcc@chromium.org>
> Cr-Commit-Position: refs/heads/master@{#525638}

TBR=eugenis@chromium.org,brettw@chromium.org,hans@chromium.org,rnk@chromium.org,pcc@chromium.org,rsesek@chromium.org
NOTRY=true

Skipping the CQ because there appear to be Android bot capacity issues.

Bug: 787920,797267
Change-Id: I3a033492561ae2ff4fcf46fe9087efbbd9f015f6
Cq-Include-Trybots: master.tryserver.chromium.android:android_arm64_dbg_recipe;master.tryserver.chromium.android:android_compile_mips_dbg;master.tryserver.chromium.android:android_compile_x64_dbg;master.tryserver.chromium.android:android_compile_x86_dbg
Reviewed-on: https://chromium-review.googlesource.com/843242
Commit-Queue: Reid Kleckner <rnk@chromium.org>
Reviewed-by: Reid Kleckner <rnk@chromium.org>
Reviewed-by: Avi Drissman <avi@chromium.org>
Cr-Original-Commit-Position: refs/heads/master@{#526072}
Cr-Mirrored-From: https://chromium.googlesource.com/chromium/src
Cr-Mirrored-Commit: bcd195d07a842f2ed3745dfa4a0a6bb341375ff5

config/BUILDCONFIG.gn

@@ -525,9 +525,6 @@ default_compiler_configs = [
   "//build/config/compiler:default_optimization",
   "//build/config/compiler:default_stack_frames",
   "//build/config/compiler:default_symbols",
-
-  # TODO(crbug.com/795158): Remove once libwidevinecdmadapter.so is fixed.
-  "//build/config/compiler:default_fatal_linker_warnings",
   "//build/config/compiler:no_exceptions",
   "//build/config/compiler:no_rtti",
   "//build/config/compiler:runtime_library",

config/compiler/BUILD.gn

@@ -265,6 +265,16 @@ config("compiler") {
         cflags += [ "-fstack-protector" ]
       }
     }
+
+    # Linker warnings.
+    if (fatal_linker_warnings && !(is_chromeos && current_cpu == "arm") &&
+        !(is_android && use_order_profiling) && !is_mac && !is_ios &&
+        current_os != "aix") {
+      # TODO(jochen): Enable this on chromeos on arm. http://crbug.com/356580
+      # TODO(lizeb,pasko): Fix link errors when linking with order_profiling=1
+      # crbug.com/485542
+      ldflags += [ "-Wl,--fatal-warnings" ]
+    }
   }
 
   # Eliminate build metadata (__DATE__, __TIME__ and __TIMESTAMP__) for
@@ -2040,19 +2050,3 @@ if (is_ios || is_mac) {
     cflags_objcc = common_flags
   }
 }
-
-# Default linker warnings.
-config("default_fatal_linker_warnings") {
-  ldflags = []
-
-  # Linker warnings.
-  if (!is_win && fatal_linker_warnings &&
-      !(is_chromeos && current_cpu == "arm") &&
-      !(is_android && use_order_profiling) && !is_mac && !is_ios &&
-      current_os != "aix") {
-    # TODO(jochen): Enable this on chromeos on arm. http://crbug.com/356580
-    # TODO(lizeb,pasko): Fix link errors when linking with order_profiling=1
-    # crbug.com/485542
-    ldflags += [ "-Wl,--fatal-warnings" ]
-  }
-}