Enable/Disable of "Select All" menu item should be represented by Document::queryCommandEnabled("SelectAll") defined in [1].

I observe:
 - always enabled: Mac TextEdit and Win Notepad.
 - wordpad: disabled for empty, enabled for non-empty even if all text is selected.

[1] src/third_party/WebKit/Source/core/editing/commands/EditorCommand.cpp

- Firefox: disabled for empty, enabled for non-empty text even if all text is selected.

The following revision refers to this bug:
  https://chromium.googlesource.com/chromium/src.git/+/c9178af4426d3a2fc543bd77e929cea2562d8d4c

commit c9178af4426d3a2fc543bd77e929cea2562d8d4c
Author: amaralp <amaralp@chromium.org>
Date: Fri Mar 17 00:09:31 2017

Select All present even all selectable text has been selected

When you right click in an empty text box "Select All" isn't grayed out. Also if you
were to use select all to select all text and then right click you "Select All"
would not be grayed out even though all text is already selected. This will also be
used in fixing Clank bug:  crbug.com/615435 

BUG= 696134 

Review-Url: https://codereview.chromium.org/2712603007
Cr-Commit-Position: refs/heads/master@{#457617}

[add] https://crrev.com/c9178af4426d3a2fc543bd77e929cea2562d8d4c/third_party/WebKit/LayoutTests/editing/selection/select_all/select_all_contenteditable.html
[add] https://crrev.com/c9178af4426d3a2fc543bd77e929cea2562d8d4c/third_party/WebKit/LayoutTests/editing/selection/select_all/select_all_input.html
[add] https://crrev.com/c9178af4426d3a2fc543bd77e929cea2562d8d4c/third_party/WebKit/LayoutTests/editing/selection/select_all/select_all_textarea.html
[modify] https://crrev.com/c9178af4426d3a2fc543bd77e929cea2562d8d4c/third_party/WebKit/Source/core/editing/commands/EditorCommand.cpp
[modify] https://crrev.com/c9178af4426d3a2fc543bd77e929cea2562d8d4c/third_party/WebKit/Source/web/ContextMenuClientImpl.cpp
[modify] https://crrev.com/c9178af4426d3a2fc543bd77e929cea2562d8d4c/third_party/WebKit/Source/web/tests/WebFrameTest.cpp

The following revision refers to this bug:
  https://chromium.googlesource.com/chromium/src.git/+/099fc50c9790b25cf3ec7bad7aed7b75a8e98c80

commit 099fc50c9790b25cf3ec7bad7aed7b75a8e98c80
Author: amaralp <amaralp@chromium.org>
Date: Fri Apr 07 05:13:43 2017

Fixing select all for contenteditable

Don't enable select all if the contenteditable has nothing to select.

BUG=  696134 

Review-Url: https://codereview.chromium.org/2787893004
Cr-Commit-Position: refs/heads/master@{#462762}

[modify] https://crrev.com/099fc50c9790b25cf3ec7bad7aed7b75a8e98c80/third_party/WebKit/LayoutTests/editing/selection/select_all/select_all_contenteditable.html
[modify] https://crrev.com/099fc50c9790b25cf3ec7bad7aed7b75a8e98c80/third_party/WebKit/Source/core/editing/commands/EditorCommand.cpp
[modify] https://crrev.com/099fc50c9790b25cf3ec7bad7aed7b75a8e98c80/third_party/WebKit/Source/web/tests/WebFrameTest.cpp