Create a new helper function to extract search terms from the URL irrespective of the availablility

chrome/browser/search/search.h

 // Copyright 2012 The Chromium Authors. All rights reserved.
 // Use of this source code is governed by a BSD-style license that can be
 // found in the LICENSE file.
 
 #ifndef CHROME_BROWSER_SEARCH_SEARCH_H_
 #define CHROME_BROWSER_SEARCH_SEARCH_H_
 
 #include <string>
 #include <utility>
 #include <vector>
@@ skipping 60 matching lines @@
 bool IsInstantExtendedAPIEnabled();
 
 // Returns whether the suggest is enabled for the given |profile|.
 bool IsSuggestPrefEnabled(Profile* profile);
 
 // Returns the value to pass to the &espv CGI parameter when loading the
 // embedded search page from the user's default search provider. Returns 0 if
 // the Instant Extended API is not enabled.
 uint64 EmbeddedSearchPageVersion();
 
-// Returns whether query extraction is enabled.
+// Returns whether query extraction flag is enabled in the field trials.
 bool IsQueryExtractionEnabled();
 
-// Extracts and returns search terms from |url|. Returns empty string if the URL
-// is not secure or doesn't have a search term replacement key.  Does not
-// consider IsQueryExtractionEnabled() and Instant support state of the page and
-// does not check for a privileged process, so most callers should use
+// Extracts and returns search terms from |url|. Does not consider
+// IsQueryExtractionEnabled() and Instant support state of the page and does
+// not check for a privileged process, so most callers should use
 // GetSearchTerms() below instead.
-base::string16 GetSearchTermsFromURL(Profile* profile, const GURL& url);
+base::string16 ExtractSearchTermsFromURL(Profile* profile, const GURL& url);
+
+// Returns true if |url| passes some basic checks that must succeed for it to be
+// usable as an instant URL:

[Jered, 2014/02/11 19:10:10]

How about rewording this comment:
"Returns true if it is ok to extract search terms from |url|. |url| must have a
secure scheme, and must contain the search terms replacement key for the default
search provider."

[kmadhusu, 2014/02/11 23:24:32]

Done.

+// (1) It contains the search terms replacement key of |template_url|, which is
+//     expected to be the TemplateURL* for the default search provider.
+// (2) Either it has a secure scheme, or else the user has manually specified a
+//     --google-base-url and it uses that base URL.  (This allows testers to use
+//     --google-base-url to point at non-HTTPS servers, which eases testing.)
+bool IsSuitableURLForInstant(Profile* profile, const GURL& url);

[kmadhusu, 2014/02/11 01:40:03]

This function deserves a better name. I would like to rename it to
IsQueryExtractionEnabledForURL. Any suggestions?

[Jered, 2014/02/11 19:10:10]

How about IsQueryExtractionAllowedForURL()?

[kmadhusu, 2014/02/11 23:24:32]

Done.

 
 // Returns the search terms attached to a specific NavigationEntry, or empty
 // string otherwise. Does not consider IsQueryExtractionEnabled() and does not
 // check Instant support, so most callers should use GetSearchTerms() below
 // instead.
 base::string16 GetSearchTermsFromNavigationEntry(
     const content::NavigationEntry* entry);
 
 // Returns search terms if this WebContents is a search results page. It looks
 // in the visible NavigationEntry first, to see if search terms have already
@@ skipping 174 matching lines @@
 bool GetBoolValueForFlagWithDefault(const std::string& flag,
                                     bool default_value,
                                     const FieldTrialFlags& flags);
 
 // Returns the Cacheable New Tab Page URL for the given |profile|.
 GURL GetNewTabPageURL(Profile* profile);
 
 }  // namespace chrome
 
 #endif  // CHROME_BROWSER_SEARCH_SEARCH_H_