build full 64bit WebView

build/config/android/config.gni

 # Copyright 2014 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 file contains common system config stuff for the Android build.
 
 if (is_android) {
   assert(rebase_path("//", root_build_dir) == "../../",
          "Android output directory must be nested 2 levels within src/ (" +
              "e.g.: out-gn/Debug). http://crbug.com/412935")
@@ skipping 115 matching lines @@
     # Disables process isolation when building _incremental targets.
     # Required for Android M+ due to SELinux policies (stronger sandboxing).
     disable_incremental_isolated_processes = false
 
     # Speed up incremental compiles by compiling only changed files.
     enable_incremental_javac = false
 
     # Adds intrumentation to each function. Writes a file with the order that
     # functions are called at startup.
     use_order_profiling = false
+
+    # Use apk_merger script to generate 64-bit WebView and Monochrome APK
+    # which has both 32-bit and 64-bit binaries.
+    merge_64bit_webview_and_monochrome = false

[Torne, 2016/09/19 13:36:28]

The description of this implies that it does the exact opposite of what it
actually does - it implies that setting this to true causes the APKs to be
merged, and that if you don't set it you don't both architectures. The name
itself also seems to suggest this, now that I'm thinking about it.

I tried to think of a better way to word this, but in the process, I realised
that I'm not sure why it's necessary to have two flags here in the first place.

What we need, both for the "buildbot that will use apk_merger.py" case, and for
the "developer who wants to skip the 32-bit build for speed" case, is a flag
that says "don't bother doing the 32-bit part of this build, just do the 64-bit
part". Why can't we just have one flag for this?

The "fast build for development" case *will* want this to apply to monochrome as
well, not just webview, as soon as we have the ability to also specify that
chrome should be 64-bit, so I don't think that's a good reason to have two
flags.

[michaelbai, 2016/09/19 21:22:26]

As Torne and I discussed offline, we came back to one variable, and give it good
name - build_android_secondary_abi, now I think build_apk_secondary_abi is
better than build_android_secondary_abi as secondary abi is meaningful in the
context of 'APK', also APK is android specific, no one should use it for other
platform.

   }
 
   # We need a second declare_args block to make sure we are using the overridden
   # value of the arguments set above.
   declare_args() {
     # Speed up dexing using dx --incremental.
     enable_incremental_dx = is_java_debug
   }
 
   # Neither of these should ever be used for release builds since they are
@@ skipping 178 matching lines @@
           "//build/toolchain/android:${android_secondary_abi_cpu}"
     }
   }
 }
 
 declare_args() {
   # Enables used resource whitelist generation. Set for official builds only
   # as a large amount of build output is generated.
   enable_resource_whitelist_generation = is_android && is_official_build
 }