[Contextual Search] Remove unused method.

Review URL: https://codereview.chromium.org/1145243011

Cr-Commit-Position: refs/heads/master@{#333134}

chrome/android/java_staging/src/org/chromium/chrome/browser/contextualsearch/ContextualSearchPolicy.java

@@ -313,16 +313,6 @@ class ContextualSearchPolicy {
         return mPreferenceManager.getContextualSearchTapCount();
     }
 
-    // --------------------------------------------------------------------------------------------
-    // Persistent "promo opens" counter.
-    // --------------------------------------------------------------------------------------------
-
-    /**
-     * Updates a persistent counter of how many times the promo was opened.
-     */
-    private void incrementPromoOpenedCount() {
-    }
-
     // --------------------------------------------------------------------------------------------
     // Private helpers.
     // --------------------------------------------------------------------------------------------