Add missing (and remove superfluous) 'explicit' from constructors.

content/browser/web_contents/navigation_controller_impl_unittest.cc

Index: content/browser/web_contents/navigation_controller_impl_unittest.cc
diff --git a/content/browser/web_contents/navigation_controller_impl_unittest.cc b/content/browser/web_contents/navigation_controller_impl_unittest.cc
index e1ef253ef78f4b23749232502efe7dba29d35ba8..9a16b4fae6d40019fcb2d84d411cc3f17d9d5b98 100644
--- a/content/browser/web_contents/navigation_controller_impl_unittest.cc
+++ b/content/browser/web_contents/navigation_controller_impl_unittest.cc
@@ -156,7 +156,7 @@ SiteInstance* GetSiteInstanceFromEntry(NavigationEntry* entry) {
 
 class TestWebContentsDelegate : public WebContentsDelegate {
  public:
-  explicit TestWebContentsDelegate() :
+  TestWebContentsDelegate() :
       navigation_state_change_count_(0) {}
 
   int navigation_state_change_count() {
@@ -944,7 +944,7 @@ TEST_F(NavigationControllerTest, Reload_GeneratesNewPage) {
 
 class TestNavigationObserver : public RenderViewHostObserver {
  public:
-  TestNavigationObserver(RenderViewHost* render_view_host)
+  explicit TestNavigationObserver(RenderViewHost* render_view_host)
       : RenderViewHostObserver(render_view_host) {
   }