capture_mode: Add ASCII art missing from previous CL

Forgot to hit save before I uploaded the previous CL at
https://chromium-review.googlesource.com/c/chromium/src/+/2339902
This is the missing ASCII art as requested in the code review.

TBR=jamescook@chromium.org
BUG=1112919

Change-Id: Ia262cfeb319106308c3cf4b1762f5c232d615cd4
Reviewed-on: https://chromium-review.googlesource.com/c/chromium/src/+/2343768Reviewed-by: James Cook <jamescook@chromium.org>
Reviewed-by: Ahmed Fakhry <afakhry@chromium.org>
Commit-Queue: Ahmed Fakhry <afakhry@chromium.org>
Cr-Commit-Position: refs/heads/master@{#796164}

ash/capture_mode/capture_mode_bar_view.h

@@ -20,6 +20,24 @@ class CaptureModeSourceView;
 class CaptureModeTypeView;
 
 // A view that acts as the content view of the capture mode bar widget.
+// It has a set of buttons to toggle between image and video capture, and
+// another set of buttons to toggle between fullscreen, region, and window
+// capture sources. The structure looks like this:
+//
+//   +--------------------------------------------------------+
+//   |  +----------------+  |                       |         |
+//   |  |  +---+  +---+  |  |  +---+  +---+  +---+  |  +---+  |
+//   |  |  |   |  |   |  |  |  |   |  |   |  |   |  |  |   |  |
+//   |  |  +---+  +---+  |  |  +---+  +---+  +---+  |  +---+  |
+//   |  +----------------+  |  ^                 ^  |  ^      |
+//   +--^----------------------|-----------------|-----|------+
+//   ^  |                      +-----------------+     |
+//   |  |                      |                       CaptureModeCloseButton
+//   |  |                      CaptureModeSourceView
+//   |  CaptureModeTypeView
+//   |
+//   CaptureModeBarView
+//
 class ASH_EXPORT CaptureModeBarView : public views::View,
                                       public views::ButtonListener {
  public: