[DevTools] Initial implementation of device modes.

Source/devtools/front_end/emulation/responsiveDesignView.css

Index: Source/devtools/front_end/emulation/responsiveDesignView.css
diff --git a/Source/devtools/front_end/emulation/responsiveDesignView.css b/Source/devtools/front_end/emulation/responsiveDesignView.css
index 1e15411fcdac1670eaeb02ebd71846a994492cee..cc552d24adcf23df95bdaa42557d04752755ac56 100644
--- a/Source/devtools/front_end/emulation/responsiveDesignView.css
+++ b/Source/devtools/front_end/emulation/responsiveDesignView.css
@@ -82,6 +82,10 @@
     transform: rotate(90deg);
 }
 
+.responsive-design-page-container {
+    background-color: #171717;
+}
+
 .responsive-design-page-scale-container {
     position: absolute !important;
     top: 0;
@@ -220,6 +224,10 @@
     cursor: default !important;
 }
 
+.device-modes .responsive-design-toolbar label {
+    margin: 0 2px;
+}
+
 .responsive-design-toolbar input[type='text'] {
     text-align: left;
     background-color: transparent;
@@ -352,10 +360,42 @@ div.responsive-design-icon:disabled {
     margin-left: 0;
 }
 
-.responsive-design-section-device select {
+.responsive-design-section-device .device-select {
     width: 185px;
 }
 
+.device-modes .responsive-design-section-device .device-select {
+    width: 145px;
+}
+
+.responsive-design-section-device .mode-container {
+    display: none;
+    width: 90px;
+}
+
+.device-modes .responsive-design-section-device .mode-container {
+    display: inline-block;
+}
+
+.responsive-design-section-device .mode-select {
+    width: 80px;
+}
+
+.responsive-design-section-device button.change-orientation-button {
+    -webkit-appearance: none;
+    background: none;
+    outline: none;
+    border: none;
+    border-radius: 3px;
+    color: rgb(255, 156, 0);
+    width: 80px;
+    margin-left: 10px;
+}
+
+.responsive-design-section-device button.change-orientation-button:hover {
+    background-color: rgba(255, 156, 0, 0.1);
+}
+
 .responsive-design-section-device input[type='text'],
 .responsive-design-section-device input[type='text']::-webkit-input-placeholder,
 .responsive-design-section-device select {