feat($compile): add support for ng-attr with camelCased attributes

SVG attributes are case sensitive and some have upper case letters in them
This change ensures that we can identify these, when being used with the `ng-attr`
directive, by encoding upper case letters with a preceding underscore.

For example to apply `ng-attr` to the `viewBox` attribute we could write
`ng-attr-view_box` - or any of the other variants: `ng:attr:view_box`,
`data-ng-attr-view_box`, etc.

Closes #9845
Closes #10194

docs/content/guide/directive.ngdoc

@@ -174,6 +174,15 @@ For example, we could fix the example above by instead writing:
 </svg>
 ```
 
+If one wants to modify a camelcased attribute (SVG elements have valid camelcased attributes), such as `viewBox` on the `svg` element, one can use underscores to denote that the attribute to bind to is naturally camelcased.
+
+For example, to bind to `viewBox`, we can write:
+
+```html
+<svg ng-attr-view_box="{{viewBox}}">
+</svg>
+```
+
 
 ## Creating Directives
 

src/ng/compile.js

@@ -1420,7 +1420,10 @@ function $CompileProvider($provide, $$sanitizeUriProvider) {
             // support ngAttr attribute binding
             ngAttrName = directiveNormalize(name);
             if (isNgAttr = NG_ATTR_BINDING.test(ngAttrName)) {
-              name = snake_case(ngAttrName.substr(6), '-');
+              name = name.replace(PREFIX_REGEXP, '')
+                .substr(8).replace(/_(.)/g, function(match, letter) {
+                  return letter.toUpperCase();
+                });
             }
 
             var directiveNName = ngAttrName.replace(/(Start|End)$/, '');

test/ng/compileSpec.js

@@ -6542,16 +6542,21 @@ describe('$compile', function() {
       expect(element.attr('href')).toBe('test/test');
     }));
 
-    it('should work if they are prefixed with x- or data-', inject(function($compile, $rootScope) {
+    it('should work if they are prefixed with x- or data- and different prefixes', inject(function($compile, $rootScope) {
       $rootScope.name = "Misko";
-      element = $compile('<span data-ng-attr-test2="{{name}}" x-ng-attr-test3="{{name}}" data-ng:attr-test4="{{name}}"></span>')($rootScope);
+      element = $compile('<span data-ng-attr-test2="{{name}}" x-ng-attr-test3="{{name}}" data-ng:attr-test4="{{name}}" ' +
+        'x_ng-attr-test5="{{name}}" data:ng-attr-test6="{{name}}"></span>')($rootScope);
       expect(element.attr('test2')).toBeUndefined();
       expect(element.attr('test3')).toBeUndefined();
       expect(element.attr('test4')).toBeUndefined();
+      expect(element.attr('test5')).toBeUndefined();
+      expect(element.attr('test6')).toBeUndefined();
       $rootScope.$digest();
       expect(element.attr('test2')).toBe('Misko');
       expect(element.attr('test3')).toBe('Misko');
       expect(element.attr('test4')).toBe('Misko');
+      expect(element.attr('test5')).toBe('Misko');
+      expect(element.attr('test6')).toBe('Misko');
     }));
 
     describe('when an attribute has a dash-separated name', function() {
@@ -6619,6 +6624,35 @@ describe('$compile', function() {
   });
 
 
+  describe('when an attribute has an underscore-separated name', function() {
+
+    it('should work with different prefixes', inject(function($compile, $rootScope) {
+      $rootScope.dimensions = "0 0 0 0";
+      element = $compile('<svg ng:attr:view_box="{{dimensions}}"></svg>')($rootScope);
+      expect(element.attr('viewBox')).toBeUndefined();
+      $rootScope.$digest();
+      expect(element.attr('viewBox')).toBe('0 0 0 0');
+    }));
+
+    it('should work if they are prefixed with x- or data-', inject(function($compile, $rootScope) {
+      $rootScope.dimensions = "0 0 0 0";
+      $rootScope.number = 0.42;
+      $rootScope.scale = 1;
+      element = $compile('<svg data-ng-attr-view_box="{{dimensions}}">' +
+        '<filter x-ng-attr-filter_units="{{number}}">' +
+        '<feDiffuseLighting data-ng:attr_surface_scale="{{scale}}">' +
+        '</feDiffuseLighting>' +
+        '<feSpecularLighting x-ng:attr_surface_scale="{{scale}}">' +
+        '</feSpecularLighting></filter></svg>')($rootScope);
+      expect(element.attr('viewBox')).toBeUndefined();
+      $rootScope.$digest();
+      expect(element.attr('viewBox')).toBe('0 0 0 0');
+      expect(element.find('filter').attr('filterUnits')).toBe('0.42');
+      expect(element.find('feDiffuseLighting').attr('surfaceScale')).toBe('1');
+      expect(element.find('feSpecularLighting').attr('surfaceScale')).toBe('1');
+    }));
+  });
+
   describe('multi-element directive', function() {
     it('should group on link function', inject(function($compile, $rootScope) {
       $rootScope.show = false;