relevant sample CL: https://chromium-review.googlesource.com/c/chromium/src/+/1171587

The following revision refers to this bug:
  https://chromium.googlesource.com/chromium/src.git/+/9385a4e282fe3ddb35a067dd68f0b1e3164e7070

commit 9385a4e282fe3ddb35a067dd68f0b1e3164e7070
Author: Ethan Xu <xuethan@chromium.org>
Date: Mon Oct 22 19:39:00 2018

[Android WebAPK] Update ShellAPK in order to support POST share targets

This CL updates the ShellAPK (but not Chrome) to support POST share targets. In particular, this
CL:
- Adds needed <meta-data> tags to AndroidManifest.xml
- Updates how the start URL is computed for share intents
- Sends activity class name of selected share target to Chrome in launch intent. Chrome needs
  this to know which share target activity to read the <meta-data> from.

BUG= 885314 

Change-Id: Ie8732a8477d722ebdb81595c602b289fab0c7a27
Reviewed-on: https://chromium-review.googlesource.com/c/1281691
Commit-Queue: Ethan Xu <xuethan@google.com>
Reviewed-by: Peter Kotwicz <pkotwicz@chromium.org>
Reviewed-by: Glenn Hartmann <hartmanng@chromium.org>
Cr-Commit-Position: refs/heads/master@{#601686}
[modify] https://crrev.com/9385a4e282fe3ddb35a067dd68f0b1e3164e7070/chrome/android/webapk/libs/common/src/org/chromium/webapk/lib/common/WebApkConstants.java
[modify] https://crrev.com/9385a4e282fe3ddb35a067dd68f0b1e3164e7070/chrome/android/webapk/libs/common/src/org/chromium/webapk/lib/common/WebApkMetaDataKeys.java
[modify] https://crrev.com/9385a4e282fe3ddb35a067dd68f0b1e3164e7070/chrome/android/webapk/shell_apk/AndroidManifest.xml
[modify] https://crrev.com/9385a4e282fe3ddb35a067dd68f0b1e3164e7070/chrome/android/webapk/shell_apk/junit/src/org/chromium/webapk/shell_apk/HostBrowserLauncherParamsTest.java
[modify] https://crrev.com/9385a4e282fe3ddb35a067dd68f0b1e3164e7070/chrome/android/webapk/shell_apk/src/org/chromium/webapk/shell_apk/HostBrowserLauncher.java
[modify] https://crrev.com/9385a4e282fe3ddb35a067dd68f0b1e3164e7070/chrome/android/webapk/shell_apk/src/org/chromium/webapk/shell_apk/HostBrowserLauncherParams.java