Adds support for attaching a market referrer.

chrome/android/java/src/org/chromium/chrome/browser/externalnav/ExternalNavigationHandler.java

Index: chrome/android/java/src/org/chromium/chrome/browser/externalnav/ExternalNavigationHandler.java
diff --git a/chrome/android/java/src/org/chromium/chrome/browser/externalnav/ExternalNavigationHandler.java b/chrome/android/java/src/org/chromium/chrome/browser/externalnav/ExternalNavigationHandler.java
index 62e7b26e134f1410c79c85b6eb56c6c04d801d72..0afeea8559af32668610bff213b24912f75d2e04 100644
--- a/chrome/android/java/src/org/chromium/chrome/browser/externalnav/ExternalNavigationHandler.java
+++ b/chrome/android/java/src/org/chromium/chrome/browser/externalnav/ExternalNavigationHandler.java
@@ -43,7 +43,12 @@ public class ExternalNavigationHandler {
     private static final String SCHEME_SMS = "sms";
 
     @VisibleForTesting
-    public static final String EXTRA_BROWSER_FALLBACK_URL = "browser_fallback_url";
+    static final String EXTRA_BROWSER_FALLBACK_URL = "browser_fallback_url";
+
+    // An extra that may be specified on an intent:// URL that contains an encoded value for the
+    // referrer field passed to the market:// URL in the case where the app is not present.
+    @VisibleForTesting
+    static final String EXTRA_MARKET_REFERRER = "market_referrer";
 
     private final ExternalNavigationDelegate mDelegate;
 
@@ -300,10 +305,19 @@ public class ExternalNavigationHandler {
             }
             String packagename = intent.getPackage();
             if (packagename != null) {
+                String marketReferrer =
+                        IntentUtils.safeGetStringExtra(intent, EXTRA_MARKET_REFERRER);
+                if (TextUtils.isEmpty(marketReferrer)) {
+                    marketReferrer = mDelegate.getPackageName();
+                }
                 try {
-                    intent = new Intent(Intent.ACTION_VIEW, Uri.parse(
-                            "market://details?id=" + packagename
-                            + "&referrer=" + mDelegate.getPackageName()));
+                    Uri marketUri = new Uri.Builder()
+                            .scheme("market")
+                            .authority("details")
+                            .appendQueryParameter("id", packagename)
+                            .appendQueryParameter("referrer", Uri.decode(marketReferrer))

[Ted C, 2016/06/13 23:27:21]

do we need to do any more sanity checking on the referrer we get?  I guess we
don't really care too much what people pass us.

And it doesn't look like Uri.decode will return null unless passed null.  I
guess android might get sad if we get passed a giant value that is too large for
intents, but that seems to be quite the stretch.

[Maria, 2016/06/13 23:46:26]

Yeah, I was thinking about this too. I figured the only thing I care about is
that it's properly encoded as a URL (e.g. no spaces), which will happen now
because Uri class auto-encodes stuff.

I suppose it could be too big, but it does seem like a stretch and won't do much
good to the person who causes that to happen, other than disincentivizing people
from clicking their links.

+                            .build();
+                    intent = new Intent(Intent.ACTION_VIEW, marketUri);
                     intent.addCategory(Intent.CATEGORY_BROWSABLE);
                     intent.setPackage("com.android.vending");
                     intent.addFlags(Intent.FLAG_ACTIVITY_NEW_TASK);