Add "lax mixed content checking" runtime flag.

Source/core/testing/InternalSettings.h

Index: Source/core/testing/InternalSettings.h
diff --git a/Source/core/testing/InternalSettings.h b/Source/core/testing/InternalSettings.h
index 3716da921b1da8ba94392e2a3b598147809a14b0..3b3b545b25e1355807b9bcf289ea148fa1a780a9 100644
--- a/Source/core/testing/InternalSettings.h
+++ b/Source/core/testing/InternalSettings.h
@@ -58,6 +58,7 @@ public:
         bool m_originalCSSExclusionsEnabled;
         bool m_originalAuthorShadowDOMForAnyElementEnabled;
         bool m_originalCSP;
+        bool m_originalLaxMixedContentCheckingEnabled;
         bool m_originalOverlayScrollbarsEnabled;
         EditingBehaviorType m_originalEditingBehavior;
         bool m_originalTextAutosizingEnabled;
@@ -116,6 +117,7 @@ public:
     void setOverlayScrollbarsEnabled(bool);
     void setExperimentalContentSecurityPolicyFeaturesEnabled(bool);
     void setPseudoClassesInMatchingCriteriaInAuthorShadowTreesEnabled(bool);
+    void setLaxMixedContentCheckingEnabled(bool);
 
     virtual void trace(Visitor*) OVERRIDE;