Port ui_base_jni_headers target to GN build.

ui/base/BUILD.gn

Index: ui/base/BUILD.gn
diff --git a/ui/base/BUILD.gn b/ui/base/BUILD.gn
index 90012e0c7c9fffe6184abadf91609ed2d675fc42..93f1534462b83f1cf27e7a5f584ec6ebfdbddfee 100644
--- a/ui/base/BUILD.gn
+++ b/ui/base/BUILD.gn
@@ -6,6 +6,7 @@ import("//build/config/ui.gni")
 
 if (is_android) {
   import("//build/config/android/config.gni")
+  import("//build/config/android/rules.gni")
 }
 
 component("ui_base") {
@@ -471,7 +472,7 @@ component("ui_base") {
     ]
 
     deps += [
-      #":ui_base_jni_headers",
+      ":ui_base_jni_headers",
     ]
 
     libs = [
@@ -540,3 +541,18 @@ source_set("ui_base_test_support") {
     ]
   }
 }
+
+if (is_android) {
+  generate_jni("ui_base_jni_headers") {
+    sources = [
+      "../android/java/src/org/chromium/ui/base/Clipboard.java",
+      "../android/java/src/org/chromium/ui/base/DeviceFormFactor.java",
+      "../android/java/src/org/chromium/ui/base/LocalizationUtils.java",
+      "../android/java/src/org/chromium/ui/base/SelectFileDialog.java",
+      "../android/java/src/org/chromium/ui/base/TouchDevice.java",
+      "../android/java/src/org/chromium/ui/base/ViewAndroid.java",
+      "../android/java/src/org/chromium/ui/base/WindowAndroid.java",
+    ]
+    jni_package = "base"
+  }
+}