Allow TranslateRanker to override decisions taken by heuristics.

components/translate/core/browser/translate_accept_languages.h

Index: components/translate/core/browser/translate_accept_languages.h
diff --git a/components/translate/core/browser/translate_accept_languages.h b/components/translate/core/browser/translate_accept_languages.h
index b296c52d2e8f911129e614213e3535ebb5101546..bad93394995f0a8f802303ce8c84195a8dd7bd78 100644
--- a/components/translate/core/browser/translate_accept_languages.h
+++ b/components/translate/core/browser/translate_accept_languages.h
@@ -34,6 +34,10 @@ class TranslateAcceptLanguages {
   // accept languages.
   bool IsAcceptLanguage(const std::string& language);
 
+ protected:
+  // Default constructor. Used for creating mocks in tests.
+  TranslateAcceptLanguages();

[groby-ooo-7-16, 2017/04/10 20:52:47]

I don't think that's necessary - see e.g MockTranslateClient

Or just set the acceptlanguage prefs?

[hamelphi, 2017/04/11 22:46:07]

Since TranslateAcceptLanguages has a non-default constructor, it needs to be
called by GMock, as far as I understand.
I tried to call the true constructor with the PrefService, but this crashes with
a segfault. 
#3 0x7f1281e7855d PrefService::GetString()
#4 0x0000044d741f translate::TranslateAcceptLanguages::InitAcceptLanguages()

I tried a bunch of ways, but could not figure out a way to correctly initialize
the TranslateAcceptLangues object. I am quite confused about what is what here.
For TranslateManager unittests, we should not require the logic from
TranslateAcceptLanguages anyway. I think that logic should be tested elsewhere.
Having this protected default constructor allows us to bypass the problematic
initialization.

[hamelphi, 2017/04/12 21:10:53]

This is not necessary anymore, since I do not call InitiateTranslation in my
unitttests.

[groby-ooo-7-16, 2017/04/20 19:45:57]

Just FYI: It crashes on GetString because the property is not registered, I
think. Any test using TranslatePrefs must register a few properties (see
existing tests)

+
  private:
   // Initializes the |accept_languages_| language table based on the associated
   // preference in |prefs|.