Fix JNI generation dependency in android_webview_unittests.

Fix JNI generation dependency in android_webview_unittests.

In the current gyp rules, the unittests depend on the following three
children: (1) java, (2) native and (3) jni generation. This is not
correct as (2) has a functional dependency on (2). Having (3) being a
sibling of (2), as it is now, introduces a race when building the
unittest target from clean.
This change fixes the problem making the jni generation step a
dependency of the native build, rather than a sibling.

BUG=None
TEST=ninja -C out/Debug android_webview_unittests_apk
NOTRY=true

Committed: https://src.chromium.org/viewvc/chrome?view=rev&revision=243426

[Primiano Tucci (use gerrit), 2014-01-06 18:51:25]

PTAL

I tested locally building from clean and seems to work reliably after the
change.

[Torne, 2014-01-07 12:35:57]

lgtm

[commit-bot: I haz the power, 2014-01-07 18:09:41]

CQ is trying da patch. Follow status at
https://chromium-status.appspot.com/cq/primiano@chromium.org/116043010/1

[commit-bot: I haz the power, 2014-01-07 22:06:04]

Retried try job too often on win_rel for step(s) browser_tests
http://build.chromium.org/p/tryserver.chromium/buildstatus?builder=win_rel&nu...

[commit-bot: I haz the power, 2014-01-07 23:09:44]

CQ is trying da patch. Follow status at
https://chromium-status.appspot.com/cq/primiano@chromium.org/116043010/1

[commit-bot: I haz the power, 2014-01-07 23:16:55]

Change committed as 243426