Fix android_webview_apk lint warnings

The video poster icon is from Honeycomb. The vector asset has been
lost in the sands of time. Replace it with a modern play icon from
www.google.com/design/icons.

Also remove the unused drawable/resource_icon.png.

BUG=241521

Review URL: https://codereview.chromium.org/1159883006

Cr-Commit-Position: refs/heads/master@{#333286}

android_webview/glue/java/src/com/android/webview/chromium/WebViewContentsClientAdapter.java

@@ -1165,10 +1165,10 @@ public Bitmap getDefaultVideoPoster() {
                 result = mWebChromeClient.getDefaultVideoPoster();
             }
             if (result == null) {
-                // The ic_media_video_poster icon is transparent so we need to draw it on a gray
-                // background.
+                // The ic_play_circle_outline_black_48dp icon is transparent so we need to draw it
+                // on a gray background.
                 Bitmap poster = BitmapFactory.decodeResource(
-                        mContext.getResources(), R.drawable.ic_media_video_poster);
+                        mContext.getResources(), R.drawable.ic_play_circle_outline_black_48dp);
                 result = Bitmap.createBitmap(
                         poster.getWidth(), poster.getHeight(), poster.getConfig());
                 result.eraseColor(Color.GRAY);