Clear parent/child tab relationships when clearing history.

Fixes http://b/issue?id=2330279
diff --git a/src/com/android/browser/BrowserActivity.java b/src/com/android/browser/BrowserActivity.java
index 462e434..a5b805f 100644
--- a/src/com/android/browser/BrowserActivity.java
+++ b/src/com/android/browser/BrowserActivity.java
@@ -3357,6 +3357,15 @@
                         }
                     }
                 }
+                // Deliberately fall through to PREFERENCES_PAGE, since the
+                // same extra may be attached to the COMBO_PAGE
+            case PREFERENCES_PAGE:
+                if (resultCode == RESULT_OK && intent != null) {
+                    String action = intent.getStringExtra(Intent.EXTRA_TEXT);
+                    if (BrowserSettings.PREF_CLEAR_HISTORY.equals(action)) {
+                        mTabControl.removeParentChildRelationShips();
+                    }
+                }
                 break;
             // Choose a file from the file picker.
             case FILE_SELECTED: