Roll Chrome into Mojo.

build/config/compiler/BUILD.gn

 # Copyright (c) 2013 The Chromium Authors. All rights reserved.
 # Use of this source code is governed by a BSD-style license that can be
 # found in the LICENSE file.
 
 import("//build/config/android/config.gni")
 if (cpu_arch == "arm") {
   import("//build/config/arm.gni")
 }
 if (cpu_arch == "mipsel" || cpu_arch == "mips64el") {
   import("//build/config/mips.gni")
@@ skipping 332 matching lines @@
       "-fPIC",
       "-pipe",  # Use pipes for communicating between sub-processes. Faster.
     ]
 
     ldflags += [
       "-fPIC",
       "-Wl,-z,noexecstack",
       "-Wl,-z,now",
       "-Wl,-z,relro",
     ]
-
-    # TODO(zork): The mipsel build is broken in ffmpeg, guard this flag for now
-    # to hide the breakage. https://crbug.com/450771
-    if (!using_sanitizer && cpu_arch != "mipsel") {
+    if (!using_sanitizer) {
       ldflags += [ "-Wl,-z,defs" ]
     }
   }
 
   # Linux-specific compiler flags setup.
   # ------------------------------------
   if (is_linux) {
     cflags += [ "-pthread" ]
     ldflags += [ "-pthread" ]
   }
@@ skipping 529 matching lines @@
 #   configs += [ "//build/config/compiler/optimize_max" ]
 
 # Shared settings for both "optimize" and "optimize_max" configs.
 if (is_win) {
   common_optimize_on_cflags = [
     "/O2",
     "/Ob2",  # both explicit and auto inlining.
     "/Oy-",  # disable omitting frame pointers, must be after /o2.
     "/Os",  # favor size over speed.
   ]
-  common_optimize_on_ldflags = []
+  if (!is_asan) {
+    common_optimize_on_cflags += [
+      # Put data in separate COMDATs. This allows the linker
+      # to put bit-identical constants at the same address even if
+      # they're unrelated constants, which saves binary size.
+      # This optimization can't be used when ASan is enabled because
+      # it is not compatible with the ASan ODR checker.
+      "/Gw",
+    ]
+  }
+  common_optimize_on_ldflags = [ "/OPT:REF" ]
 } else {
   common_optimize_on_cflags = [
     # Don't emit the GCC version ident directives, they just end up in the
     # .comment section taking up binary size.
     "-fno-ident",
 
     # Put data and code in their own sections, so that unused symbols
     # can be removed at link time with --gc-sections.
     "-fdata-sections",
     "-ffunction-sections",
@@ skipping 14 matching lines @@
     if (symbol_level == 2) {
       # Mac dead code stripping requires symbols.
       common_optimize_on_ldflags += [ "-Wl,-dead_strip" ]
     }
   } else {
     # Non-Mac Posix linker flags.
     common_optimize_on_ldflags += [
       # Specifically tell the linker to perform optimizations.
       # See http://lwn.net/Articles/192624/ .
       "-Wl,-O1",
-      "-Wl,--as-needed",
       "-Wl,--gc-sections",
     ]
+
+    if (!using_sanitizer) {
+      # Functions interposed by the sanitizers can make ld think
+      # that some libraries aren't needed when they actually are,
+      # http://crbug.com/234010. As workaround, disable --as-needed.
+      common_optimize_on_ldflags += [ "-Wl,--as-needed" ]
+    }
   }
 }
 
 # Default "optimization on" config. On Windows, this favors size over speed.
 config("optimize") {
   cflags = common_optimize_on_cflags
   ldflags = common_optimize_on_ldflags
   if (is_win) {
     cflags += [ "/Os" ]  # favor size over speed.
   } else if (is_android || is_ios) {
@@ skipping 86 matching lines @@
       cflags += [ "-gsplit-dwarf" ]
     }
   }
 }
 
 config("no_symbols") {
   if (!is_win) {
     cflags = [ "-g0" ]
   }
 }