Add WebAPK installation metrics.

chrome/browser/android/banners/app_banner_infobar_delegate_android.h

Index: chrome/browser/android/banners/app_banner_infobar_delegate_android.h
diff --git a/chrome/browser/android/banners/app_banner_infobar_delegate_android.h b/chrome/browser/android/banners/app_banner_infobar_delegate_android.h
index 6e09f1b5ad2a846be7a6aa4ef067bb33bc59dabd..6679af541ee2e66ba6dd3c4bc705c8974d28f124 100644
--- a/chrome/browser/android/banners/app_banner_infobar_delegate_android.h
+++ b/chrome/browser/android/banners/app_banner_infobar_delegate_android.h
@@ -27,6 +27,14 @@ struct ShortcutInfo;
 
 namespace banners {
 
+// The states of WebAPK installation process. These states are tracked to
+// record dismiss events for WebAPK installation.
+enum InstallState {

[dominickn, 2016/09/19 01:38:39]

Nit: call this WebApkInstallState, and change the comment to:

"The state of a WebAPK installation, where the infobar is displayed during the
entire installation process. This state is used to correctly record UMA
metrics".


Second nit: consider making this enum a private member of
AppBannerInfoBarDelegate, since it's an implementation detail. The method in the
anonymous namespace of the cc file can also move to the private area of the
class.

[Xi Han, 2016/09/20 18:25:18]

Done.

+  WAIT_FOR_START,

[dominickn, 2016/09/19 01:38:39]

Nit: "INSTALL_NOT_STARTED"?

[Xi Han, 2016/09/20 18:25:18]

Done.

+  INSTALLING,
+  INSTALLED,
+};
+
 // Manages installation of an app being promoted by a page.
 class AppBannerInfoBarDelegateAndroid : public ConfirmInfoBarDelegate {
  public:
@@ -132,6 +140,8 @@ class AppBannerInfoBarDelegateAndroid : public ConfirmInfoBarDelegate {
 
   std::string webapk_package_name_;
   bool is_webapk_;
+  // Indicates the current state of a WebAPK installation.

[dominickn, 2016/09/19 01:38:39]

Nit: add a newline above the comment.

[Xi Han, 2016/09/20 18:25:18]

Done.

+  InstallState install_state_;
 
   base::WeakPtrFactory<AppBannerInfoBarDelegateAndroid> weak_ptr_factory_;