GN: Don't compile battor_agent, imagediff, bitmaptools on Android

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.
 
 # This is the root build file for GN. GN will start processing by loading this
 # file, and recursively load all dependencies until all dependencies are either
 # resolved or known not to exist (which will cause the build to fail). So if
 # you add a new build file, there must be some path of dependencies from this
 # file to your new one or GN won't know about it.
 
@@ skipping 178 matching lines @@
       "//third_party/WebKit/Source/platform:blink_heap_unittests",
       "//third_party/WebKit/Source/platform:blink_platform_unittests",
       "//third_party/WebKit/Source/web:webkit_unit_tests",
       "//third_party/WebKit/Source/wtf:wtf_unittests",
       "//third_party/mojo/src/mojo/edk/system:mojo_system_unittests",
       "//third_party/mojo/src/mojo/edk/test:mojo_public_bindings_unittests",
       "//third_party/mojo/src/mojo/edk/test:mojo_public_environment_unittests",
       "//third_party/mojo/src/mojo/edk/test:mojo_public_system_unittests",
       "//third_party/mojo/src/mojo/edk/test:mojo_public_utility_unittests",
       "//third_party/smhasher:pmurhash",
-      "//tools/battor_agent",
-      "//tools/imagediff($host_toolchain)",
-      "//tools/telemetry:bitmaptools($host_toolchain)",
       "//ui/display:display_unittests",
       "//ui/events:events_unittests",
       "//ui/gl:gl_unittests",
       "//ui/touch_selection:ui_touch_selection_unittests",
     ]
   } else {
     deps += [
       "//ios/net:ios_net_unittests",
       "//ios/public/provider/web",
       "//ios/testing:ocmock_support_unittest",
       "//ios/web:ios_web_unittests",
       "//ios/web/shell:ios_web_shell",
     ]
 
     if (ios_use_webrtc) {
       deps += [
         "//ios/chrome:ios_chrome_unittests",
         "//ios/chrome/app",
         "//ios/chrome/browser",
         "//ios/chrome/common",
         "//ios/public/provider/chrome/browser",
       ]
     }
   }
 
+  # Tools that are relevant only on the host.
+  if (is_mac || is_win || is_linux) {
+    deps += [
+      "//tools/battor_agent",
+      "//tools/imagediff($host_toolchain)",
+      "//tools/telemetry:bitmaptools($host_toolchain)",

[Dirk Pranke, 2015/12/23 21:19:32]

I don't think this change is right. 

You definitely still need to build imagediff and bitmaptools when
target_os==android, you just need to build the host versions (as it says).

I suspect that's true for battor_agent as well, so may the right thing to do is
to change that to have ($host_toolchain)?

[agrieve, 2015/12/28 19:46:07]

Hmm, guess my brain wasn't working correctly :P. I've put back imagediff and
bitmaptools. I tried marking battor_agent as $host_toolchain, but that actually
fails to gn gen due to inconsistencies in how use_gconf is set. Rather than
fixing that, I took it as a sign that battor_agent isn't needed for is_android
and left it in this separate block.

[charliea (OOO until 10-5), 2016/01/04 15:38:37]

Yep - you're right in that battor agent is only needed for desktop builds. The
agent is a tracing tool that communicates from a desktop to a connected device
that's measuring power consumption.

+    ]
+  }
+
   deps += root_extra_deps
 
   if (enable_extensions) {
     deps += [ "//extensions/shell:app_shell_unittests" ]
   }
 
   if (enable_media_router) {
     deps += [ "//chrome/browser/media/router" ]
   }
 
@@ skipping 620 matching lines @@
       ]
 
       if (target_cpu == "x86") {
         deps += [ "//chrome/tools/crash_service:crash_service_win64" ]
       }
     } else {
       deps += [ "//breakpad:minidump_stackwalk($host_toolchain)" ]
     }
   }
 }