fix(tooltip): performance and scope fixes

Isolate scope contents should be the same after hiding and showing the
tooltip. The isolate scope's parent should also always be set to the
directive's scope correctly.

fix(tooltip): link on demand

- Calling $digest is enough as we only need to digest the watchers in
  this scope and its children. No need to call $apply.

- Set invokeApply to false on $timeout for popUpDelay

- No need to test for cached reference when tooltip isn't visible as
  the tooltip has no scope.

Closes #1450
Closes #1191
Closes #1455

src/tooltip/test/tooltip.spec.js

@@ -98,7 +98,7 @@ describe('tooltip', function() {
     scope.alt = "Alt Message";
 
     elmBody = $compile( angular.element( 
-      '<div><span alt={{alt}} tooltip="{{tooltipMsg}}">Selector Text</span></div>' 
+      '<div><span alt={{alt}} tooltip="{{tooltipMsg}}" tooltip-animation="false">Selector Text</span></div>'
     ) )( scope );
 
     $compile( elmBody )( scope );
@@ -114,6 +114,13 @@ describe('tooltip', function() {
     expect( ttScope.content ).toBe( scope.tooltipMsg );
 
     elm.trigger( 'mouseleave' );
+
+    //Isolate scope contents should be the same after hiding and showing again (issue 1191)
+    elm.trigger( 'mouseenter' );
+
+    ttScope = angular.element( elmBody.children()[1] ).scope();
+    expect( ttScope.placement ).toBe( 'top' );
+    expect( ttScope.content ).toBe( scope.tooltipMsg );
   }));
 
   it('should not show tooltips if there is nothing to show - issue #129', inject(function ($compile) {
@@ -136,6 +143,24 @@ describe('tooltip', function() {
     expect( elmBody.children().length ).toBe( 0 );
   }));
 
+  it('issue 1191 - isolate scope on the popup should always be child of correct element scope', inject( function ( $compile ) {
+    var ttScope;
+    elm.trigger( 'mouseenter' );
+
+    ttScope = angular.element( elmBody.children()[1] ).scope();
+    expect( ttScope.$parent ).toBe( elmScope );
+
+    elm.trigger( 'mouseleave' );
+
+    // After leaving and coming back, the scope's parent should be the same
+    elm.trigger( 'mouseenter' );
+
+    ttScope = angular.element( elmBody.children()[1] ).scope();
+    expect( ttScope.$parent ).toBe( elmScope );
+
+    elm.trigger( 'mouseleave' );
+  }));
+
   describe('with specified enable expression', function() {
 
     beforeEach(inject(function ($compile) {
@@ -323,18 +348,12 @@ describe('tooltip', function() {
 
       elm = elmBody.find('input');
       elmScope = elm.scope();
+      elm.trigger('fooTrigger');
       tooltipScope = elmScope.$$childTail;
     }));
 
-    it( 'should not contain a cached reference', function() {
-      expect( inCache() ).toBeTruthy();
-      elmScope.$destroy();
-      expect( inCache() ).toBeFalsy();
-    });
-
     it( 'should not contain a cached reference when visible', inject( function( $timeout ) {
       expect( inCache() ).toBeTruthy();
-      elm.trigger('fooTrigger');
       elmScope.$destroy();
       expect( inCache() ).toBeFalsy();
     }));