adjust demo styling

Author: andrewseguin

src/demo-app/tooltip/tooltip-demo.html

@@ -1,8 +1,8 @@
 <div class="demo-tooltip">
   <h1>Tooltip Demo</h1>
 
-  <div class="centered" style="height: 200px; width: 400px; overflow: auto; padding: 200px" cdk-scrollable>
-    <button #tooltip="mdTooltip" style="margin-bottom: 300px;"
+  <div class="centered" cdk-scrollable>
+    <button #tooltip="mdTooltip"
             md-raised-button
             color="primary"
             [mdTooltip]="message"
@@ -11,7 +11,8 @@ <h1>Tooltip Demo</h1>
             [mdTooltipHideDelay]="hideDelay">
       Mouse over to see the tooltip
     </button>
-    Scroll down while tooltip is open to see it hide automatically
+    <div>Scroll down while tooltip is open to see it hide automatically</div>
+    <div style="height: 400px;"></div>
   </div>
 
   <p>

src/demo-app/tooltip/tooltip-demo.scss

@@ -1,6 +1,12 @@
 .demo-tooltip {
   .centered {
     text-align: center;
+    height: 200px;
+    overflow: auto;
+
+    button {
+      margin: 16px;
+    }
   }
   md-radio-button {
     display: block;

src/lib/tooltip/tooltip.ts

@@ -39,7 +39,7 @@ export type TooltipPosition = 'left' | 'right' | 'above' | 'below' | 'before' |
 export const TOUCHEND_HIDE_DELAY  = 1500;
 
 /** Time in ms to throttle repositioning after scroll events. */
-export const SCROLL_THROTTLE_MS = 20;
+export const SCROLL_THROTTLE_MS = 10;
 
 /**
  * Directive that attaches a material design tooltip to the host element. Animates the showing and
@@ -186,7 +186,8 @@ export class MdTooltip implements OnInit, OnDestroy {
     let strategy = this._overlay.position().connectedTo(this._elementRef, origin, position);
     strategy.withScrollableContainers(this._scrollDispatcher.getScrollContainers(this._elementRef));
     strategy.onPositionChange.subscribe(change => {
-      if (change.scrollableViewProperties.isOverlayClipped && this._tooltipInstance.isVisible()) {
+      if (change.scrollableViewProperties.isOverlayClipped &&
+          this._tooltipInstance && this._tooltipInstance.isVisible()) {
         this.hide(0);
       }
     });