[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 00edefc201128a69b6078e18d14be4f630a2792e..d67cf9032ea3996ccc85cc8c8760d7b016bcb432 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-art .responsive-design-toolbar label {
+    margin: 0 2px;
+}
+
 .responsive-design-toolbar input[type='text'] {
     text-align: left;
     background-color: transparent;
@@ -298,6 +306,10 @@
     top: 3px;
 }
 
+.device-art .responsive-design-icon {
+    margin: 0 3px;
+}
+
 div.responsive-design-icon:disabled {
     opacity: 1 !important;
 }
@@ -340,6 +352,10 @@ div.responsive-design-icon:disabled {
     margin-left: 1px;
 }
 
+.device-art .responsive-design-icon-swap {
+    margin: 0 4px;
+}
+
 .responsive-design-icon-swap:hover {
     background-color: rgb(255, 180, 0);
 }
@@ -389,10 +405,27 @@ div.responsive-design-icon:disabled {
     margin-left: 0;
 }
 
-.responsive-design-section-device select {
+.responsive-design-section-device .device-select {
     width: 185px;
 }
 
+.device-art .responsive-design-section-device .device-select {
+    width: 145px;
+}
+
+.responsive-design-section-device .mode-select {
+    display: none;
+    width: 120px;
+}
+
+.device-art .responsive-design-section-device .mode-select {
+    display: initial;
+}
+
+.responsive-design-section-device .mode-select.invisible {
+    visibility: hidden;
+}
+
 .responsive-design-section-device input[type='text'],
 .responsive-design-section-device input[type='text']::-webkit-input-placeholder,
 .responsive-design-section-device select {