Update messages and element-name.

1. Update checkbox messages to improve accessibility.
2. Use 'toggle' only on checkbox to avoid confusion.

BUG=chromium:878257
TEST=Tested by showing tooltips and using ChromeVox on buttons.

Change-Id: I69bdb3e5d894966c06c8807e537c3b502a331be6
Reviewed-on: https://chromium-review.googlesource.com/c/1275927
Reviewed-by: Sheng-hao Tsao <shenghao@google.com>
Tested-by: yuli <yuli@chromium.org>
diff --git a/Makefile b/Makefile
index 0585f63..efb4db8 100644
--- a/Makefile
+++ b/Makefile
@@ -73,11 +73,11 @@
 	src/images/camera_button_mic_on.svg \
 	src/images/camera_button_mirror_off.svg \
 	src/images/camera_button_mirror_on.svg \
+	src/images/camera_button_switch_device.svg \
 	src/images/camera_button_switch_photo.svg \
 	src/images/camera_button_switch_video.svg \
 	src/images/camera_button_timer_off.svg \
 	src/images/camera_button_timer_on.svg \
-	src/images/camera_button_toggle_device.svg \
 	src/images/camera_focus_aim.svg \
 	src/images/camera_mode_photo.svg \
 	src/images/camera_mode_recording.svg \
diff --git a/src/_locales/en/messages.json b/src/_locales/en/messages.json
index ae6c331..6dad0a3 100644
--- a/src/_locales/en/messages.json
+++ b/src/_locales/en/messages.json
@@ -89,13 +89,9 @@
     "message": "Stop recording",
     "description": "Label for the shutter button to stop recording."
   },
-  "toggleTimerButton": {
-    "message": "Toggle timer",
-    "description": "Label for the button to toggle the countdown timer."
-  },
-  "toggleCameraButton": {
-    "message": "Toggle camera",
-    "description": "Label for the button to switch between multiple cameras. Eg. switching from front facing to back facing, or a camera connected via USB. The button is shown only when more than one camera is connected."
+  "switchCameraButton": {
+    "message": "Switch to next camera",
+    "description": "Label for the button to switch to next connected camera. Eg. switching from front facing to back facing, or a camera connected via USB. The button is shown only when more than one camera is connected."
   },
   "switchRecordVideoButton": {
    "message": "Switch to record video",
@@ -105,17 +101,21 @@
    "message": "Switch to take photo",
    "description": "Label for the button to switch to take photo mode."
   },
+  "toggleTimerButton": {
+    "message": "Timer",
+    "description": "Label for the checkbox to toggle the countdown timer."
+  },
   "toggleMirrorButton": {
-    "message": "Toggle mirroring",
-    "description": "Label for the button to toggle the preview mirroring."
+    "message": "Mirroring",
+    "description": "Label for the checkbox to toggle the preview mirroring."
   },
   "toggleGridButton": {
-    "message": "Toggle grid",
-    "description": "Label for the button to toggle the grid shown on preview."
+    "message": "Grid",
+    "description": "Label for the checkbox to toggle the grid shown on preview."
   },
   "toggleMicButton": {
-    "message": "Toggle microphone",
-    "description": "Label for the button to toggle the microphone for recording video."
+    "message": "Microphone",
+    "description": "Label for the checkbox to toggle the microphone for recording video."
   },
   "dialogOKButton": {
     "message": "OK",
diff --git a/src/css/main.css b/src/css/main.css
index b379d45..7a54fc7 100644
--- a/src/css/main.css
+++ b/src/css/main.css
@@ -370,17 +370,17 @@
   visibility: visible;
 }
 
-#toggle-device {
-  background-image: url(../images/camera_button_toggle_device.svg);
+#switch-device {
+  background-image: url(../images/camera_button_switch_device.svg);
   width: 48px;
   height: 48px;
 }
 
-#toggle-device.animate {
-  animation: toggle-device-rotate 350ms ease-out;
+#switch-device.animate {
+  animation: switch-device-rotate 350ms ease-out;
 }
 
-@keyframes toggle-device-rotate {
+@keyframes switch-device-rotate {
   0% {
     transform: rotate(0deg);
   }
diff --git a/src/images/camera_button_toggle_device.svg b/src/images/camera_button_switch_device.svg
similarity index 100%
rename from src/images/camera_button_toggle_device.svg
rename to src/images/camera_button_switch_device.svg
diff --git a/src/js/views/camera/options.js b/src/js/views/camera/options.js
index f3dcfc0..19b4ee6 100644
--- a/src/js/views/camera/options.js
+++ b/src/js/views/camera/options.js
@@ -67,7 +67,7 @@
    * @type {HTMLButtonElement}
    * @private
    */
-  this.toggleDevice_ = document.querySelector('#toggle-device');
+  this.switchDevice_ = document.querySelector('#switch-device');
 
   /**
    * @type {HTMLButtonElement}
@@ -140,8 +140,8 @@
       'click', this.onSwitchRecordVideoClicked_.bind(this));
   this.switchTakePhoto_.addEventListener(
       'click', this.onSwitchTakePhotoClicked_.bind(this));
-  this.toggleDevice_.addEventListener(
-      'click', this.onToggleDeviceClicked_.bind(this));
+  this.switchDevice_.addEventListener(
+      'click', this.onSwitchDeviceClicked_.bind(this));
   this.toggleMirror_.addEventListener(
       'click', this.onToggleMirrorClicked_.bind(this));
   this.toggleGrid_.addEventListener(
@@ -225,7 +225,7 @@
   this.toggleMic_.disabled = disabled;
 
   disabled = disabled || taking;
-  this.toggleDevice_.disabled = disabled;
+  this.switchDevice_.disabled = disabled;
   this.switchRecordVideo_.disabled = disabled;
   this.switchTakePhoto_.disabled = disabled;
 };
@@ -264,13 +264,13 @@
 };
 
 /**
- * Handles clicking on the toggle camera device switch.
+ * Handles clicking on the camera device switch.
  * @param {Event} event Click event.
  * @private
  */
-camera.views.camera.Options.prototype.onToggleDeviceClicked_ = function(event) {
+camera.views.camera.Options.prototype.onSwitchDeviceClicked_ = function(event) {
   this.videoDeviceIds_.then(deviceIds => {
-    camera.util.animateOnce(this.toggleDevice_);
+    camera.util.animateOnce(this.switchDevice_);
     var index = deviceIds.indexOf(this.videoDeviceId_);
     if (index == -1) {
       index = 0;
@@ -497,10 +497,10 @@
 
   // Update UI options.
   this.videoDeviceIds_.then(deviceIds => {
-    this.toggleDevice_.hidden = deviceIds.length < 2;
+    this.switchDevice_.hidden = deviceIds.length < 2;
   }).catch(error => {
     console.error(error);
-    this.toggleDevice_.hidden = true;
+    this.switchDevice_.hidden = true;
   }).finally(() => {
     this.refreshingVideoDeviceIds_ = false;
   });
diff --git a/src/views/main.html b/src/views/main.html
index 9f65de7..641614d 100644
--- a/src/views/main.html
+++ b/src/views/main.html
@@ -53,8 +53,8 @@
                 i18n-label="switchRecordVideoButton"></button>
       </div>
       <div class="bottom-stripe left-stripe buttons circle">
-        <button id="toggle-device" disabled tabindex="0"
-                i18n-label="toggleCameraButton" hidden></button>
+        <button id="switch-device" disabled tabindex="0"
+                i18n-label="switchCameraButton" hidden></button>
       </div>
       <div class="bottom-stripe right-stripe buttons circle">
         <button id="gallery-enter" disabled tabindex="0"