Use DCHECKs when observing only a single notification.

chrome/browser/android/tab_web_contents_delegate_android.cc

Index: chrome/browser/android/tab_web_contents_delegate_android.cc
diff --git a/chrome/browser/android/tab_web_contents_delegate_android.cc b/chrome/browser/android/tab_web_contents_delegate_android.cc
index 19d6e52a5c14e554aa37ec9b29783cb62a8c3a40..81f87c8c36ef1e3c09f55b6ef5126a339dc2c808 100644
--- a/chrome/browser/android/tab_web_contents_delegate_android.cc
+++ b/chrome/browser/android/tab_web_contents_delegate_android.cc
@@ -165,16 +165,10 @@ void TabWebContentsDelegateAndroid::Observe(
     int type,
     const content::NotificationSource& source,
     const content::NotificationDetails& details) {
-  switch (type) {
-    case chrome::NOTIFICATION_FIND_RESULT_AVAILABLE:
-      OnFindResultAvailable(
-          content::Source<WebContents>(source).ptr(),
-          content::Details<FindNotificationDetails>(details).ptr());
-      break;
-    default:
-      NOTREACHED() << "Unexpected notification: " << type;
-      break;
-  }
+  DCHECK_EQ(chrome::NOTIFICATION_FIND_RESULT_AVAILABLE, type);
+  OnFindResultAvailable(
+      content::Source<WebContents>(source).ptr(),
+      content::Details<FindNotificationDetails>(details).ptr());
 }
 
 blink::WebDisplayMode TabWebContentsDelegateAndroid::GetDisplayMode(