Photo Picker Dialog: Add window enter animation.

chrome/android/java/res/values-v21/styles.xml

Index: chrome/android/java/res/values-v21/styles.xml
diff --git a/chrome/android/java/res/values-v21/styles.xml b/chrome/android/java/res/values-v21/styles.xml
index 51ade3405969e369b38eabd84c1623a975cba809..b1f666f26b129457ea4d4e14f95909dc67d183a2 100644
--- a/chrome/android/java/res/values-v21/styles.xml
+++ b/chrome/android/java/res/values-v21/styles.xml
@@ -139,4 +139,11 @@
              half is way brighter than the bottom), so we use our own. -->
         <item name="android:textCursorDrawable">@drawable/text_cursor_lowend</item>
     </style>
+
+    <!-- Photo Picker animations -->
+
+    <style name="PhotoPickerDialogAnimation">
+        <item name="android:windowEnterAnimation">@anim/design_bottom_sheet_slide_in</item>

[Theresa, 2017/05/12 15:29:40]

v21 is only used on Lollipop and higher. This should be defined in v17.

+        <item name="android:windowExitAnimation">@null</item>
+    </style>
 </resources>