Enable whole-program virtual function optimization in LTO mode.

build/config/sanitizers/BUILD.gn

Index: build/config/sanitizers/BUILD.gn
diff --git a/build/config/sanitizers/BUILD.gn b/build/config/sanitizers/BUILD.gn
index 33497235a58613ae9eb6b58d9b894ef255dbe835..29bb7f1c03f05e0152cc1daa74502fe8bac23919 100644
--- a/build/config/sanitizers/BUILD.gn
+++ b/build/config/sanitizers/BUILD.gn
@@ -94,36 +94,13 @@ config("default_sanitizer_ldflags") {
     if (is_ubsan_vptr) {
       ldflags += [ "-fsanitize=vptr" ]
     }
-    if (is_lto && !is_nacl) {
-      ldflags += [ "-flto" ]
-
-      # Apply a lower LTO optimization level as the default is too slow.
-      if (is_linux) {
-        ldflags += [ "-Wl,-plugin-opt,O1" ]
-      } else if (is_mac) {
-        ldflags += [ "-Wl,-mllvm,-O1" ]
-      }
-
-      # Work-around for http://openradar.appspot.com/20356002
-      if (is_mac) {
-        ldflags += [ "-Wl,-all_load" ]
-      }
-
-      # Without this flag, LTO produces a .text section that is larger
-      # than the maximum call displacement, preventing the linker from
-      # relocating calls (http://llvm.org/PR22999).
-      if (current_cpu == "arm") {
-        ldflags += [ "-Wl,-plugin-opt,-function-sections" ]
-      }
-
-      if (is_cfi) {
-        ldflags += [
-          "-fsanitize=cfi-vcall",
-          "-fsanitize=cfi-derived-cast",
-          "-fsanitize=cfi-unrelated-cast",
-        ]
-      }
 
+    if (is_cfi && !is_nacl) {
+      ldflags += [
+        "-fsanitize=cfi-vcall",
+        "-fsanitize=cfi-derived-cast",
+        "-fsanitize=cfi-unrelated-cast",
+      ]
       if (use_cfi_diag) {
         ldflags += [
           "-fno-sanitize-trap=cfi",
@@ -156,7 +133,7 @@ config("default_sanitizer_flags") {
 
   # Common options for AddressSanitizer, LeakSanitizer, ThreadSanitizer,
   # MemorySanitizer and non-official CFI builds.
-  if (using_sanitizer || (is_lto && !is_official_build)) {
+  if (using_sanitizer || (is_cfi && !is_official_build)) {
     if (is_posix) {
       cflags += [ "-fno-omit-frame-pointer" ]
     } else {
@@ -282,19 +259,15 @@ config("default_sanitizer_flags") {
       "-fsanitize-blacklist=$ubsan_blacklist_path",
     ]
   }
-  if (is_lto && !is_nacl) {
-    cflags += [ "-flto" ]
-
-    if (is_cfi) {
-      cfi_blacklist_path =
-          rebase_path("//tools/cfi/blacklist.txt", root_build_dir)
-      cflags += [
-        "-fsanitize=cfi-vcall",
-        "-fsanitize=cfi-derived-cast",
-        "-fsanitize=cfi-unrelated-cast",
-        "-fsanitize-blacklist=$cfi_blacklist_path",
-      ]
-    }
+  if (is_cfi && !is_nacl) {
+    cfi_blacklist_path =
+        rebase_path("//tools/cfi/blacklist.txt", root_build_dir)
+    cflags += [
+      "-fsanitize=cfi-vcall",
+      "-fsanitize=cfi-derived-cast",
+      "-fsanitize=cfi-unrelated-cast",
+      "-fsanitize-blacklist=$cfi_blacklist_path",
+    ]
 
     if (use_cfi_diag) {
       cflags += [