Update assets/accessible name on back button

BUG=749713
TEST=manual

Change-Id: I05908a8761336bf6bb8daf24e40201536ab16c40
Reviewed-on: https://chromium-review.googlesource.com/876940Reviewed-by: Ahmed Fakhry <afakhry@chromium.org>
Commit-Queue: Mitsuru Oshima <oshima@chromium.org>
Cr-Commit-Position: refs/heads/master@{#530658}

ash/ash_strings.grd

@@ -1220,6 +1220,11 @@ Subsequent notifications, windows and dialogs may be split between desktops.
       <message name="IDS_ASH_MESSAGE_CENTER_NO_NOTIFIERS" desc="The message displayed in the message center when there are no notification sources.">
         Nothing to see just yet
       </message>
+
+      <!-- Window Control -->
+      <message name="IDS_ASH_WINDOW_CONTROL_ACCNAME_BACK" desc="The accessible name for the back button on the window frame.">
+        Back button
+      </message>
     </messages>
   </release>
 </grit>

ash/frame/caption_buttons/frame_back_button.cc

@@ -7,8 +7,11 @@
 #include "ash/ash_layout_constants.h"
 #include "ash/frame/caption_buttons/frame_caption_button.h"
 #include "ash/resources/vector_icons/vector_icons.h"
+#include "ash/strings/grit/ash_strings.h"
 #include "ui/aura/window.h"
 #include "ui/aura/window_tree_host.h"
+#include "ui/base/l10n/l10n_util.h"
+#include "ui/base/resource/resource_bundle.h"
 #include "ui/events/event_sink.h"
 #include "ui/views/widget/widget.h"
 
@@ -18,6 +21,8 @@ FrameBackButton::FrameBackButton()
     : FrameCaptionButton(this, CAPTION_BUTTON_ICON_BACK) {
   SetImage(CAPTION_BUTTON_ICON_BACK, ANIMATE_NO, kWindowControlBackIcon);
   SetPreferredSize(GetAshLayoutSize(AshLayoutSize::NON_BROWSER_CAPTION_BUTTON));
+  SetAccessibleName(
+      l10n_util::GetStringUTF16(IDS_ASH_WINDOW_CONTROL_ACCNAME_BACK));
 }
 
 FrameBackButton::~FrameBackButton() = default;

ash/resources/vector_icons/window_control_back.1x.icon

@@ -4,15 +4,16 @@
 
 CANVAS_DIMENSIONS, 12,
 FLIPS_IN_RTL,
-MOVE_TO, 3.9f, 5.25f,
-H_LINE_TO, 11.25f,
-R_V_LINE_TO, 1.5f,
-H_LINE_TO, 3.9f,
-R_LINE_TO, 4.6, 3.6f,
-LINE_TO, 6.68f, 11.25f,
-LINE_TO, 1.5f, 6,
-R_LINE_TO, 5.18f, -5.25f,
-LINE_TO, 7.5f, 1.65f,
-LINE_TO, 3.9f, 5.25f,
+MOVE_TO, 4.92f, 5,
+H_LINE_TO, 11,
+R_V_LINE_TO, 2,
+H_LINE_TO, 4.92f,
+LINE_TO, 8, 9.75f,
+LINE_TO, 6.6f, 11,
+LINE_TO, 1, 6,
+R_LINE_TO, 0.7f, -0.62f,
+LINE_TO, 6.6f, 1,
+LINE_TO, 8, 2.25f,
+LINE_TO, 4.92f, 5,
 CLOSE,
 END

ash/resources/vector_icons/window_control_back.icon

@@ -4,14 +4,17 @@
 
 CANVAS_DIMENSIONS, 24,
 FLIPS_IN_RTL,
-MOVE_TO, 6.42f, 13.49f,
-R_LINE_TO, 7.24f, 7.49f,
-LINE_TO, 12.14f, 22.5f,
-LINE_TO, 2.25f, 12.37f,
-LINE_TO, 12.14f, 2.25f,
-R_LINE_TO, 1.52, 1.5f,
-R_LINE_TO, -7.4f, 7.49f,
-H_LINE_TO, 21.75,
-R_V_LINE_TO, 2.25f,
+MOVE_TO, 6.83f, 10,
+H_LINE_TO, 23,
+R_V_LINE_TO, 3,
+H_LINE_TO, 6.83f,
+LINE_TO, 15, 20.96f,
+LINE_TO, 12.86f, 23,
+LINE_TO, 4.93f, 15.25f,
+LINE_TO, 1, 11.5f,
+R_LINE_TO, 5, -4.77f,
+LINE_TO, 12.86f, 0,
+LINE_TO, 15, 2.05f,
+LINE_TO, 6.83f, 10,
 CLOSE,
 END