Record document mode histogram in UMA on every upload.

chrome/android/java/src/org/chromium/chrome/browser/util/FeatureUtilities.java

Index: chrome/android/java/src/org/chromium/chrome/browser/util/FeatureUtilities.java
diff --git a/chrome/android/java/src/org/chromium/chrome/browser/util/FeatureUtilities.java b/chrome/android/java/src/org/chromium/chrome/browser/util/FeatureUtilities.java
index 38bce66ccb2edaa13799ede7446dceac85082053..422d51b69e2d72c495524f5ad8ead7a9ac6f093e 100644
--- a/chrome/android/java/src/org/chromium/chrome/browser/util/FeatureUtilities.java
+++ b/chrome/android/java/src/org/chromium/chrome/browser/util/FeatureUtilities.java
@@ -84,4 +84,14 @@ public class FeatureUtilities {
         Bundle userRestrictions = manager.getUserRestrictions();
         return !userRestrictions.getBoolean(UserManager.DISALLOW_MODIFY_ACCOUNTS, false);
     }
+
+    /**
+     * Records the current document mode state with native-side feature utilities.
+     * @param enabled Whether the document mode is enabled.
+     */
+    public static void setDocumentModeEnabled(boolean enabled) {
+        nativeSetDocumentModeEnabled(enabled);
+    }
+
+    private static native void nativeSetDocumentModeEnabled(boolean enabled);
 }