Make Android-specific LTO disablements have effect only on Android.

Also add a TODO requested by Nico.

BUG=453195
R=thakis@chromium.org
CC=fdegans@chromium.org

Review URL: https://codereview.chromium.org/880403005

Cr-Commit-Position: refs/heads/master@{#313803}

build/android/disable_lto.gypi

@@ -8,7 +8,7 @@
   'target_conditions': [
     ['_toolset=="target"', {
       'conditions': [
-        ['use_lto==1 or use_lto_o2==1', {
+        ['OS=="android" and (use_lto==1 or use_lto_o2==1)', {
           'cflags!': [
             '-flto',
             '-ffat-lto-objects',

build/android/increase_size_for_speed.gypi

@@ -22,13 +22,13 @@
             # LTO merges all optimization options at link-time. -O2 takes
             # precedence over -Os. Avoid using LTO simultaneously
             # on -Os and -O2 parts for that reason.
-            ['use_lto==1', {
+            ['OS=="android" and use_lto==1', {
               'cflags!': [
                 '-flto',
                 '-ffat-lto-objects',
               ],
             }],
-            ['use_lto_o2==1', {
+            ['OS=="android" and use_lto_o2==1', {
               'cflags': [
                 '-flto',
                 '-ffat-lto-objects',

build/common.gypi

@@ -2985,7 +2985,8 @@
       }],
       ['use_lto==1 and (target_arch=="ia32" or target_arch=="x64")', {
         # Required for third_party/zlib/crc_folding.c and various other code
-        # that uses SSE.
+        # that uses SSE. TODO(pcc): Remove this once we properly support
+        # subtarget specific code generation in LLVM.
         'ldflags': ['-Wl,-plugin-opt,mcpu=corei7-avx'],
       }],
     ],  # conditions for 'target_defaults'