added UnityWebViewPostprocessBuild.cs for Android.

build/Rakefile

@@ -36,6 +36,7 @@ SRCS[0]=%W|
   WebViewObject.cs
   iOS/WebView.mm
   iOS/Editor/UnityWebViewPostprocessBuild.cs
+  Android/Editor/UnityWebViewPostprocessBuild.cs
 |
 
 # NOTE: WebPlayerTemplates is not inclued for now because the sample app becomes complicated.

plugins/Android/Editor/UnityWebViewPostprocessBuild.cs

@@ -0,0 +1,51 @@
+#if UNITY_ANDROID
+using System.Collections;
+using System.IO;
+using System.Xml;
+using UnityEditor.Callbacks;
+using UnityEditor;
+using UnityEngine;
+
+public class UnityWebViewPostprocessBuild {
+    // you need to modify ACTIVITY_NAME if you utilize any custom activty.
+    private const string ACTIVITY_NAME = "com.unity3d.player.UnityPlayerActivity";
+
+    [PostProcessBuild(100)]
+    public static void OnPostprocessBuild(BuildTarget buildTarget, string path) {
+        if (buildTarget == BuildTarget.Android) {
+            string manifest = Path.Combine(Application.dataPath, "Plugins/Android/AndroidManifest.xml");
+            if (!File.Exists(manifest)) {
+                string manifest0 = Path.Combine(Application.dataPath, "../Temp/StagingArea/AndroidManifest-main.xml");
+                if (!File.Exists(manifest0)) {
+                    Debug.LogError("cannot find both Assets/Plugins/Android/AndroidManifest.xml and Temp/StagingArea/AndroidManifest-main.xml. please build the app to generate Assets/Plugins/Android/AndroidManifest.xml and then rebuild it again.");
+                    return;
+                } else {
+                    File.Copy(manifest0, manifest);
+                }
+            }
+            XmlDocument doc = new XmlDocument();
+            doc.Load(manifest);
+            XmlElement activity = null;
+            // Let's find the application node.
+            foreach (XmlNode node0 in doc.DocumentElement.ChildNodes) {
+                if (node0.Name == "application") {
+                    foreach (XmlNode node1 in node0.ChildNodes) {
+                        if (node1.Name == "activity"
+                            && ((XmlElement)node1).GetAttribute("android:name") == ACTIVITY_NAME) {
+                            activity = (XmlElement)node1;
+                            break;
+                        }
+                    }
+                    break;
+                }
+            }
+            if (activity != null
+                && string.IsNullOrEmpty(activity.GetAttribute("android:hardwareAccelerated"))) {
+                activity.SetAttribute("hardwareAccelerated", "http://schemas.android.com/apk/res/android", "true");
+                doc.Save(manifest);
+                Debug.LogError("adjusted AndroidManifest.xml about android:hardwareAccelerated. Please rebuild the app.");
+            }
+        }
+    }
+}
+#endif