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 bb9e030916de819706c9df62fcac2f8e18429aad..6e11cc1ec9e31d23566c864094dd5735e3927e10 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"
@@ -341,6 +344,14 @@ void WebApkInstaller::OnURLFetchComplete(const net::URLFetcher* source) {
     OnFailure();
     return;
   }
+
+  if (base::FeatureList::IsEnabled(chrome::android::kPlayInstallWebApks)){
+    InstallWebApkFromPlayStore(response->package_name(),
+                               std::atoi(response->version().c_str()),
+                               response->token());

[pkotwicz, 2016/11/24 22:59:20]

Ideally, Google Play installs will work when:
- Google Play installs are enabled via variations
- The user is not using chrome_public_apk

Perhaps we should subclass WebApkInstaller, GooglePlayWebApkInstaller perhaps?

+    return;
+  }
+
   OnGotWebApkDownloadUrl(signed_download_url, response->package_name());
 }
 
@@ -412,6 +423,22 @@ 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;