Devtools Animations: Add cubic bezier easing editor for animations

Source/devtools/front_end/elements/animationTimeline.css

Index: Source/devtools/front_end/elements/animationTimeline.css
diff --git a/Source/devtools/front_end/elements/animationTimeline.css b/Source/devtools/front_end/elements/animationTimeline.css
index 100658bac3f40e9ceb98ca369cd9966a4fc90e1d..0bf82134470fbbeb28eca572922fed2328312719 100644
--- a/Source/devtools/front_end/elements/animationTimeline.css
+++ b/Source/devtools/front_end/elements/animationTimeline.css
@@ -59,6 +59,10 @@ circle.animation-endpoint:hover, circle.animation-keyframe-point:hover {
     transform: scale(1.2);
 }
 
+.animation-tail-iterations circle.animation-endpoint:hover, .animation-tail-iterations circle.animation-keyframe-point:hover {
+    transform: scale(1);
+}
+
 circle.animation-endpoint:active, circle.animation-keyframe-point:active {
     transform: scale(1);
 }
@@ -76,6 +80,7 @@ circle.animation-keyframe-point {
     text-overflow: ellipsis;
     overflow: hidden;
     white-space: nowrap;
+    min-width: 45px;
 }
 
 .animation-timeline-header {
@@ -282,7 +287,7 @@ svg.animation-ui g:first-child {
     opacity: 1;
 }
 
-.animation-tail-iterations {
+g {
     opacity: 0.5;
 }
 
@@ -314,4 +319,40 @@ text.animation-timeline-grid-label {
 
 .animation-node-row.animation-node-selected {
     background-color: hsla(218, 78%, 66%, 0.1);
-}
+}
+
+.bezier-icon {
+    width: 14px;
+    height: 14px;
+    background-color: #9C27B0;
+    position: absolute;
+    top: 13px;
+    border-radius: 2px;
+    opacity: 0;
+    z-index: 10;
+    padding: 2px;
+    left: -30px;
+    transition: opacity 100ms cubic-bezier(0, 0, 0.2, 1);
+    transition-delay: 500ms;
+}
+
+.bezier-icon.shown {
+    opacity: 0.3;
+    transition-delay: 0s;
+}
+
+.bezier-icon.bezier-editor-open {
+    opacity: 1.0 !important;
+}
+
+.bezier-icon:hover {
+    opacity: 1.0;
+    transition-delay: 0s;
+}
+
+.bezier-icon path {
+    stroke: white;
+    stroke-width: 1.5;
+    stroke-linecap: square;
+    fill: none;
+}