Update Select-to-Speak description strings per UI writer feedback.

Bug: 849893
Change-Id: Iaf8c30493e383e754940afbb928994c9ffcd12fd
Reviewed-on: https://chromium-review.googlesource.com/1087325
Commit-Queue: Katie Dektar <katie@chromium.org>
Reviewed-by: Hector Carmona <hcarmona@chromium.org>
Cr-Commit-Position: refs/heads/master@{#564929}

chrome/app/settings_strings.grdp

@@ -337,13 +337,13 @@
     <message name="IDS_SETTINGS_ACCESSIBILITY_SELECT_TO_SPEAK_TITLE" desc="In the settings tab, the text next to the checkbox to enable an option to hold a key and click to speak any on-screen text out loud.">
       Enable select-to-speak
     </message>
-    <message name="IDS_SETTINGS_ACCESSIBILITY_SELECT_TO_SPEAK_DISABLED_DESCRIPTION" desc="In the settings tab, the description a feature which will read on-screen text out loud, shown when that feature is disabled.">
+    <message name="IDS_SETTINGS_ACCESSIBILITY_SELECT_TO_SPEAK_DISABLED_DESCRIPTION" desc="In the settings tab, the description of a feature that will read on-screen text out loud. This text is shown when that feature is disabled.">
       Hear text read aloud
     </message>
-    <message name="IDS_SETTINGS_ACCESSIBILITY_SELECT_TO_SPEAK_DESCRIPTION" desc="In the settings tab, the description of an option to hold a key and click or drag a box with the mouse to speak any on-screen text out loud.">
-      Highlight what you want to hear, then press Search + S. Or, press and hold search, or tap the Select-to-Speak icon near your profile image, then select a region to be read aloud.
+    <message name="IDS_SETTINGS_ACCESSIBILITY_SELECT_TO_SPEAK_DESCRIPTION" desc="For devices with a hardware keyboard. In the settings tab, the description of an option to hold a key and click or drag a box with the mouse to speak any on-screen text out loud.">
+      Highlight what you want to hear, then press Search + S. You can also press and hold the Search key, or tap the Select-to-Speak icon near your profile image to make a selection.
     </message>
-    <message name="IDS_SETTINGS_ACCESSIBILITY_SELECT_TO_SPEAK_DESCRIPTION_WITHOUT_KEYBOARD" desc="In the settings tab, the description of an option tap a button and drag a box with the mouse, stylus or touch to speak any on-screen text out loud.">
+    <message name="IDS_SETTINGS_ACCESSIBILITY_SELECT_TO_SPEAK_DESCRIPTION_WITHOUT_KEYBOARD" desc="For devices that do not have a hardware keyboard. In the settings tab, the description of an option to highlight text to be read out loud.">
       Tap the Select-to-Speak icon near your profile image, then select what you want to hear.
     </message>
     <message name="IDS_SETTINGS_ACCESSIBILITY_SELECT_TO_SPEAK_OPTIONS_LABEL" desc="In the settings tab, the label for the button that opens the Options page for the Select-to-Speak feature.">