Port gfx_jni_headers target to GN build.

ui/gfx/BUILD.gn

Index: ui/gfx/BUILD.gn
diff --git a/ui/gfx/BUILD.gn b/ui/gfx/BUILD.gn
index 9a3463d6a3bbffacbd269afa99a1b85fc4937adc..ea1a2defdd088917bc114822f6655e96b78ba3e3 100644
--- a/ui/gfx/BUILD.gn
+++ b/ui/gfx/BUILD.gn
@@ -3,8 +3,10 @@
 # found in the LICENSE file.
 
 import("//build/config/ui.gni")
+
 if (is_android) {
   import("//build/config/android/config.gni")
+  import("//build/config/android/rules.gni")
 }
 
 # Several targets want to include this header file, and some of them are
@@ -286,7 +288,7 @@ component("gfx") {
       deps += [ "//base:base_java" ]
     }
 
-    deps += [ ":jni_headers" ]
+    deps += [ ":gfx_jni_headers" ]
     libs = [
       "android",
       "jnigraphics",
@@ -496,7 +498,14 @@ test("gfx_unittests") {
 }
 
 if (is_android) {
-  # TODO(brettw) gfx_jni_headers
+  generate_jni("gfx_jni_headers") {
+    sources = [
+      "../android/java/src/org/chromium/ui/gfx/BitmapHelper.java",
+      "../android/java/src/org/chromium/ui/gfx/DeviceDisplayInfo.java",
+      "../android/java/src/org/chromium/ui/gfx/ViewConfigurationHelper.java",
+    ]
+    jni_package = "gfx"
+  }
 }
 
 if (use_x11) {