build full 64bit WebView

build/config/android/config.gni

Index: build/config/android/config.gni
diff --git a/build/config/android/config.gni b/build/config/android/config.gni
index 6a16eb2d68bc82f3c147fcd0ec9e2c2247297525..aec30a83ef2675a9727780f05e6ff1634ac25075 100644
--- a/build/config/android/config.gni
+++ b/build/config/android/config.gni
@@ -133,6 +133,9 @@ if (is_android) {
     # Adds intrumentation to each function. Writes a file with the order that
     # functions are called at startup.
     use_order_profiling = false
+
+    # Only build 64-bit binaries in 64-bit WebView APK.

[Torne, 2016/09/16 14:04:18]

Maybe "Only build 64-bit binaries in 64-bit WebView APK. 32-bit apps will not be
supported; for development only." to be a bit more explicit that this isn't the
"right" thing to do for shipping?

[michaelbai, 2016/09/16 16:14:22]

Done.

+    build_64bit_only_webview = false
   }
 
   # We need a second declare_args block to make sure we are using the overridden
@@ -142,6 +145,11 @@ if (is_android) {
     enable_incremental_dx = is_java_debug
   }
 
+  if (defined(merge_64bit_webview_and_monochrome) &&

[Torne, 2016/09/16 14:04:18]

I think you should also just declare this variable upstream as well. There's
nothing secret about the ability to build the two parts of the APK separately
and then merge them; anyone with a similar CI infrastructure could conceivably
prefer to do it that way.

[michaelbai, 2016/09/16 16:14:22]

It is not for hiding something, I think this should be internal only, here are
some reasons 
- without internal code, no one could build Monochrome (We don't have public
monochrome yet), 
-  for the people want to merge 64-bit SystemWebView.apk, they can do it without
setting this variable.
- to have it in upstream might confuse people, as it is same as
build_64bit_only_webview when people only have upstream code. they might wonder
why I have to set this variable as I already set build_64bit_only_webview,
what's the difference between them?. If people can NOT find it in gn args
--list, they don't need to worry about it. this is beauty of GN variable scope.
:)

Do we want to tell people how to merge 64-bit SystemWebView.apk? If so, we
should have document for it, maybe just add it in apk_merger script.

 

[Torne, 2016/09/16 16:35:33]

But we will at some point.
The rule of thumb should be that everything is public unless there is a specific
reason why it needs to be internal (confidentiality, or a dependency on another
internal thing). I don't think it matters whether it's actually useful right now
or not. It *will* be useful when there's a public monochrome target, so why not
just define it now instead of having to do a two-sided patch later to move it?
Yes, we should probably at least have the script contain an explanation of how
to build the two "half" APKs and merge them together. I don't think it needs to
be documented anywhere else in particular; most people will just use the
self-contained combined build and that's a sensible default.

[michaelbai, 2016/09/16 20:05:55]

Fair enough, everything is in public

+      merge_64bit_webview_and_monochrome) {
+    build_64bit_only_webview = true
+  }
+
   # Neither of these should ever be used for release builds since they are
   # somewhat experimental and dx --incremental is known to not produce
   # byte-for-byte identical output.