Chrome talks to Play to install WebAPKs.

chrome/browser/android/webapk/webapk_installer.cc

Index: chrome/browser/android/webapk/webapk_installer.cc
diff --git a/chrome/browser/android/webapk/webapk_installer.cc b/chrome/browser/android/webapk/webapk_installer.cc
index 4bb94ba61ca12602c6d366c8835ed3e59f1b6f7a..7c40df10a4ee6df585818b49dbf8a6afdb665d12 100644
--- a/chrome/browser/android/webapk/webapk_installer.cc
+++ b/chrome/browser/android/webapk/webapk_installer.cc
@@ -4,6 +4,8 @@
 
 #include "chrome/browser/android/webapk/webapk_installer.h"
 
+#include <stdlib.h>
+
 #include "base/android/build_info.h"
 #include "base/android/jni_android.h"
 #include "base/android/jni_string.h"
@@ -22,6 +24,7 @@
 #include "chrome/browser/android/webapk/webapk.pb.h"
 #include "chrome/browser/android/webapk/webapk_icon_hasher.h"
 #include "chrome/browser/profiles/profile.h"
+#include "chrome/common/chrome_switches.h"
 #include "components/variations/variations_associated_data.h"
 #include "components/version_info/version_info.h"
 #include "content/public/browser/browser_thread.h"
@@ -328,6 +331,15 @@ void WebApkInstaller::OnURLFetchComplete(const net::URLFetcher* source) {
     OnFailure();
     return;
   }
+
+  if (base::CommandLine::ForCurrentProcess()->HasSwitch(
+      switches::kEnablePlayInstallWebApk)) {
+    InstallWebApkFromPlayStore(response->package_name(),
+                               std::atoi(response->version().c_str()),

[pkotwicz, 2016/11/23 03:11:28]

Random thought: Why isn't the version part of the token?

[Xi Han, 2016/11/23 15:43:46]

Scott confirmed that the token is just a random number and doesn't contain any
other information, all the useful information is cached on the server.
Personally, I would prefer to keep the version as a separate field like now.

[pkotwicz, 2016/11/23 15:56:38]

I dislike that the token is a random number. If it's truly random, than there is
a small chance of collisions and it is possible for a person to install a
different WebAPK than they intended. Can it be the WebAPK id with a random
number appended to it?

I still don't understand why passing the version to Google Play is important. Is
passing the version number a "Google Play requirement" or a "WebAPK server
requirement"?

[Xi Han, 2016/11/23 16:44:42]

As discussed offline, the version is required by Play, and we keep it as it is
now.

+                               response->token());
+    return;
+  }
+
   OnGotWebApkDownloadUrl(signed_download_url, response->package_name());
 }
 
@@ -399,6 +411,22 @@ void WebApkInstaller::SendRequest(std::unique_ptr<webapk::WebApk> request_proto,
   url_fetcher_->Start();
 }
 
+void WebApkInstaller::InstallWebApkFromPlayStore(
+    const std::string& package_name, int version, const std::string& token) {
+  webapk_package_ = package_name;
+
+  JNIEnv* env = base::android::AttachCurrentThread();
+  base::android::ScopedJavaLocalRef<jstring> java_webapk_package =
+      base::android::ConvertUTF8ToJavaString(env, webapk_package_);
+  base::android::ScopedJavaLocalRef<jstring> java_title =
+      base::android::ConvertUTF16ToJavaString(env, shortcut_info_.user_title);
+  base::android::ScopedJavaLocalRef<jstring> java_token =
+      base::android::ConvertUTF8ToJavaString(env, token);
+
+  Java_WebApkInstaller_installWebApkFromPlayStoreAsyncAndMonitorInstallation(
+      env, java_ref_, java_webapk_package, version, java_title, java_token);
+}
+
 void WebApkInstaller::OnGotWebApkDownloadUrl(const GURL& download_url,
                                              const std::string& package_name) {
   webapk_package_ = package_name;