Author: Olivier Tilloy <olivier.tilloy@canonical.com>
Description: Do not use warning flags that require a newer Clang

Index: dev/build/config/compiler/BUILD.gn
===================================================================
--- build/config/compiler/BUILD.gn
+++ build/config/compiler/BUILD.gn
@@ -693,14 +693,6 @@ config("compiler") {
     ldflags += [ "-Wl,--no-rosegment" ]
   }
 
-  # This flag enforces that member pointer base types are complete. It helps
-  # prevent us from running into problems in the Microsoft C++ ABI (see
-  # https://crbug.com/847724).
-  if (is_clang && !is_nacl && target_os != "chromeos" && !use_xcode_clang &&
-      (is_win || use_custom_libcxx)) {
-    cflags += [ "-fcomplete-member-pointers" ]
-  }
-
   # Pass the same C/C++ flags to the objective C/C++ compiler.
   cflags_objc += cflags_c
   cflags_objcc += cflags_cc
@@ -1501,28 +1493,6 @@ config("default_warnings") {
       if (current_toolchain == host_toolchain || !use_xcode_clang) {
         # Flags NaCl (Clang 3.7) and Xcode 9.2 (Clang clang-900.0.39.2) do not
         # recognize.
-        cflags += [
-          # Ignore warnings about MSVC optimization pragmas.
-          # TODO(thakis): Only for no_chromium_code? http://crbug.com/912662
-          "-Wno-ignored-pragma-optimize",
-
-          # TODO(https://crbug.com/989932): Evaluate and possibly enable.
-          "-Wno-implicit-int-float-conversion",
-
-          # TODO(https://crbug.com/999871): Decide if we want to clean up the
-          # codebase or just disable this.  Doesn't seem super useful, but
-          # also fires in only 4 files.
-          "-Wno-c99-designator",
-
-          # This is a side effect of -Wc99-designator; easier to clean up.
-          "-Wno-reorder-init-list",
-
-          # TODO(https://crbug.com/999886): Clean up, enable.
-          "-Wno-final-dtor-non-final-class",
-
-          # TODO(https://crbug.com/1002945): Evaluate and possibly enable.
-          "-Wno-sizeof-array-div",
-        ]
 
         cflags_c += [
           # TODO(https://crbug.com/995993): Clean up and enable.