media_controls: Add UI for showing a promo bubble on a control button.

third_party/WebKit/Source/core/css/mediaControls.css

Index: third_party/WebKit/Source/core/css/mediaControls.css
diff --git a/third_party/WebKit/Source/core/css/mediaControls.css b/third_party/WebKit/Source/core/css/mediaControls.css
index 90ae832568c036e5abbd02c16065614844daab19..2b201dfe3f5c4358b042cf2ddaaf8172c8743f71 100644
--- a/third_party/WebKit/Source/core/css/mediaControls.css
+++ b/third_party/WebKit/Source/core/css/mediaControls.css
@@ -72,7 +72,7 @@ audio::-webkit-media-controls-panel, video::-webkit-media-controls-panel {
     position: relative;
     width: 100%;
     z-index: 0;
-    overflow: hidden;
+    overflow: visible;
     text-align: right;
     bottom: auto;
     height: 32px;
@@ -513,13 +513,24 @@ video::-internal-media-controls-overflow-button, audio::-internal-media-controls
     color: inherit;
 }
 
-video::-internal-media-controls-download-button, audio::-internal-media-controls-download-button {
-    -webkit-appearance: -internal-media-download-button;
+video::-internal-media-controls-download-button-container, audio::-internal-media-controls-download-button-container {
     display: flex;
     flex: none;
+    position: relative;
     box-sizing: border-box;
     width: 32px;
     height: 32px;
+    background-color: initial;
+    color: inherit;
+}
+
+video::-internal-media-controls-download-button, audio::-internal-media-controls-download-button {
+    -webkit-appearance: -internal-media-download-button;
+    display: flex;
+    flex: none;
+    box-sizing: border-box;
+    width: inherit;
+    height: inherit;
     padding: 0px;
     border-width: 0px;
     margin-left: 0px;
@@ -609,3 +620,73 @@ video::cue(u) {
 video::cue(i) {
     font-style: italic;
 }
+
+video::-internal-media-controls-promo-container {
+    display: flex;
+    flex: none;
+    position: absolute;
+    left: 0px;
+    top: 0px;
+    box-sizing: border-box;
+    z-index: 42;
+    width: inherit;
+    height: inherit;
+    background-color: initial;
+    color: inherit;
+    pointer-events: none;
+}
+
+@keyframes -internal-media-controls-promo-throbbing {

[Khushal, 2017/05/20 01:48:08]

For some reason, this doesn't seem to be working. I can't find it in the
inspector either. I'm not sure but might be related to crbug.com/486195.

[Khushal, 2017/05/22 18:19:32]

I figured what's going on with this one. Potential fix is here:
https://codereview.chromium.org/2895913002/

+    0%    {transform: scale(0.5, 0.5);}
+    50%   {transform: scale(1.0, 1.0);}
+    100%  {transform: scale(0.5, 0.5);}
+}
+
+video::-internal-media-controls-promo-animation {
+    display: flex;
+    flex: none;
+    box-sizing: border-box;
+    width: inherit;
+    height: inherit;
+    border-radius: 50%;
+    background-color: #4285f4;
+    color: blue;
+    opacity: 0.4;
+    animation: -internal-media-controls-download-promo-throbbing 2s infinite;
+}
+
+video::-internal-media-controls-promo-arrow {
+    display: flex;
+    flex: none;
+    box-sizing: border-box;
+    position: absolute;
+    top: 100%;
+    left: 50%;
+    margin-left: -10px;
+    margin-top: -10px;
+    width: 0px;
+    height: 0px;
+    border-top: 10px solid transparent;
+    border-left: 10px solid transparent;
+    border-right: 10px solid transparent;
+    border-bottom: 10px solid #4285f4;
+}
+
+video::-internal-media-controls-promo-text {
+    display: inline-block;
+    flex: none;
+    position: absolute;
+    background: #5285f4;
+    color: #fff;
+    font-family: sans-serif;
+    padding: 16px;
+    top: 100%;
+    right: 0%;
+    margin-top: 10px;
+    z-index: 42;
+    border-radius: 2px;
+    font-size: 14px;
+    color: white;
+    white-space: nowrap;
+    line-height: 100%;
+}