Add the Play Store app search to the launcher.

components/arc/common/app.mojom

Index: components/arc/common/app.mojom
diff --git a/components/arc/common/app.mojom b/components/arc/common/app.mojom
index 6348d52517e4851ebe484d466b77707bf5585eb3..b1e474b9e5caf99fed58542c0c743f76a200fee0 100644
--- a/components/arc/common/app.mojom
+++ b/components/arc/common/app.mojom
@@ -2,7 +2,7 @@
 // Use of this source code is governed by a BSD-style license that can be
 // found in the LICENSE file.
 //
-// Next MinVersion: 20
+// Next MinVersion: 21
 
 module arc.mojom;
 
@@ -75,6 +75,19 @@ enum ShowPackageInfoPage {
   MANAGE_LINKS = 1,
 };
 
+// Describes a Play Store app discovery result.
+struct AppDiscoveryResult {
+  string? launch_intent_uri;
+  string? install_intent_uri;

[dcheng, 2017/06/24 00:16:47]

Are these actual URLs? We're consuming them in Chrome right? What does an intent
URL do? What are we doing with them?

(Also, normally, we'd just use url.mojom.Url to represent URLs, but 1) maybe the
intent URIs don't fit into that and 2) I guess ARC++ is trying to limit its
dependencies on non-ARC++ structs)

[Jiaquan He, 2017/06/24 00:48:08]

A launch_intent_uri here is used to start an Android activity, which looks like
"#Intent;component=com.android.browser/com.android.BrowserActivity;end"

An install_intent_uri is used to guide the user to a Play Store installation
page of an Android application, which is an URL and looks like
"https://play.google.com/store/apps/details?id=shu.gear.data#Intent;package=com.android.vending;component=com.android.vending/com.google.android.finsky.appdiscoveryservice.AppDiscoveryLaunchActivity;l.com.google.android.finsky.analytics.LoggingContext.KEY_LAST_EVENT_ID=699526169;S.com.google.android.finsky.analytics.LoggingContext.KEY_USE_DEFAULT_LOGGER=true;i.sessionId=0;i.requestCode=8;i.callingVersionCode=25;S.callingPackageName=org.chromium.arc.gms;end".

Other ARC++ interfaces are also using "string" for these intents.

[dcheng, 2017/06/24 00:58:28]

OK, I think it's still worth having a discussion about these, but that's out of
scope of this CL.

+  string? label;
+  bool is_instant_app;
+  bool is_recent;
+  string? publisher_name;
+  string? formatted_price;
+  float review_score;
+  array<uint8> icon_png_data;
+};
+
 // Next method ID: 18
 interface AppHost {
   // Sends newly added ARC app to Chrome. This message is sent when ARC receives
@@ -161,7 +174,7 @@ interface AppHost {
 };
 
 // TODO(lhchavez): Migrate all request/response messages to Mojo.
-// Next method ID: 16
+// Next method ID: 17
 // Deprecated method ID: 9
 interface AppInstance {
   Init@0(AppHost host_ptr);
@@ -233,4 +246,9 @@ interface AppInstance {
   // Sends a request to ARC to uninstall the given package.  Error (if ever
   // happens) is ignored, and uninstall option should appear in the UI.
   [MinVersion=2] UninstallPackage@5(string package_name);
+
+  // Starts a query for Play Store apps.
+  [MinVersion=20] GetRecentAndSuggestedAppsFromPlayStore@16(
+      string query, int32 max_results) =>
+          (array<AppDiscoveryResult> results);
 };