fix(tooltip): always append to body and disappear on scroll

- Default animation origin has been set to bottom that mean the origin is `top center`

Closes #6140

src/components/tooltip/tooltip.js

@@ -58,18 +58,19 @@ function MdTooltipDirective($timeout, $window, $$rAF, $document, $mdUtil, $mdThe
 
     var parent        = $mdUtil.getParentWithPointerEvents(element),
         content       = angular.element(element[0].getElementsByClassName('md-content')[0]),
-        current       = $mdUtil.getNearestContentElement(element),
-        tooltipParent = angular.element(current || document.body),
+        tooltipParent = angular.element(document.body),
         debouncedOnResize = $$rAF.throttle(function () { updatePosition(); });
 
+    if ($animate.pin) $animate.pin(element, parent);
+
     // Initialize element
 
     setDefaults();
     manipulateElement();
     bindEvents();
 
-    // Default origin transform point is 'left top'
-    // positionTooltip() is always relative to top left
+    // Default origin transform point is 'center top'
+    // positionTooltip() is always relative to center top
     updateContentOrigin();
 
     configureWatchers();
@@ -81,7 +82,7 @@ function MdTooltipDirective($timeout, $window, $$rAF, $document, $mdUtil, $mdThe
     }
 
     function updateContentOrigin() {
-      var origin = 'left top';
+      var origin = 'center top';
       switch (scope.direction) {
         case 'left'  : origin =  'right center';  break;
         case 'right' : origin =  'left center';   break;
@@ -137,19 +138,25 @@ function MdTooltipDirective($timeout, $window, $$rAF, $document, $mdUtil, $mdThe
         });
 
         attributeObserver.observe(parent[0], { attributes: true});
-      };
+      }
 
       // Store whether the element was focused when the window loses focus.
       var windowBlurHandler = function() {
         elementFocusedOnWindowBlur = document.activeElement === parent[0];
       };
       var elementFocusedOnWindowBlur = false;
 
+      function windowScrollHandler() {
+        setVisible(false);
+      }
+
       ngWindow.on('blur', windowBlurHandler);
       ngWindow.on('resize', debouncedOnResize);
+      document.addEventListener('scroll', windowScrollHandler, true);
       scope.$on('$destroy', function() {
         ngWindow.off('blur', windowBlurHandler);
         ngWindow.off('resize', debouncedOnResize);
+        document.removeEventListener('scroll', windowScrollHandler, true);
         attributeObserver && attributeObserver.disconnect();
       });
 

src/components/tooltip/tooltip.scss

@@ -48,6 +48,7 @@ md-tooltip {
     &.md-show, &.md-show-add-active {
       transform: scale(1);
       opacity: 1;
+      transform-origin: center top;
     }
     &.md-show-remove {
       transition: $swift-ease-out;