[Chromecast] Get board name in CastSysInfoAndroid.

Need a board name for Widevine's CDM.

BUG=internal 62721854
TEST=

Change-Id: I79850985dd11f29dc60f911f7bb5070d47e8efa5
Reviewed-on: https://chromium-review.googlesource.com/572225
Commit-Queue: Thoren Paulson <thoren@chromium.org>
Reviewed-by: Luke Halliwell <halliwell@chromium.org>
Cr-Commit-Position: refs/heads/master@{#487132}

chromecast/base/cast_sys_info_android.cc

@@ -82,7 +82,9 @@ std::string CastSysInfoAndroid::GetSystemReleaseChannel() {
 }
 
 std::string CastSysInfoAndroid::GetBoardName() {
-  return "";
+  JNIEnv* env = base::android::AttachCurrentThread();
+  return base::android::ConvertJavaStringToUTF8(
+      Java_CastSysInfoAndroid_getBoard(env));
 }
 
 std::string CastSysInfoAndroid::GetBoardRevision() {

chromecast/browser/android/apk/src/org/chromium/chromecast/shell/CastSysInfoAndroid.java

@@ -22,4 +22,10 @@ public final class CastSysInfoAndroid {
     private static String getSerialNumber() {
         return Build.SERIAL;
     }
+
+    @SuppressLint("HardwareIds")
+    @CalledByNative
+    private static String getBoard() {
+        return Build.BOARD;
+    }
 }