feat($http): remove deprecated callback methods: `success()/error()`

Closes #15157

BREAKING CHANGE:

`$http`'s deprecated custom callback methods - `success()` and `error()` - have been removed.
You can use the standard `then()`/`catch()` promise methods instead, but note that the method
signatures and return values are different.

`success(fn)` can be replaced with `then(fn)`, and `error(fn)` can be replaced with either
`then(null, fn)` or `catch(fn)`.

Before:

```js
$http(...).
  success(function onSuccess(data, status, headers, config) {
    // Handle success
    ...
  }).
  error(function onError(data, status, headers, config) {
    // Handle error
    ...
  });
```

After:

```js
$http(...).
  then(function onSuccess(response) {
    // Handle success
    var data = response.data;
    var status = response.status;
    var statusText = response.statusText;
    var headers = response.headers;
    var config = response.config;
    ...
  }, function onError(response) {
    // Handle error
    var data = response.data;
    var status = response.status;
    var statusText = response.statusText;
    var headers = response.headers;
    var config = response.config;
    ...
  });

// or

$http(...).
  then(function onSuccess(response) {
    // Handle success
    var data = response.data;
    var status = response.status;
    var statusText = response.statusText;
    var headers = response.headers;
    var config = response.config;
    ...
  }).
  catch(function onError(response) {
    // Handle error
    var data = response.data;
    var status = response.status;
    var statusText = response.statusText;
    var headers = response.headers;
    var config = response.config;
    ...
  });
```

**Note:**
There is a subtle difference between the variations showed above. When using
`$http(...).success(onSuccess).error(onError)` or `$http(...).then(onSuccess, onError)`, the
`onError()` callback will only handle errors/rejections produced by the `$http()` call. If the
`onSuccess()` callback produces an error/rejection, it won't be handled by `onError()` and might go
unnoticed. In contrast, when using `$http(...).then(onSuccess).catch(onError)`, `onError()` will
handle errors/rejections produced by both `$http()` _and_ `onSuccess()`.

src/ng/http.js

@@ -9,11 +9,6 @@ var JSON_ENDS = {
 };
 var JSON_PROTECTION_PREFIX = /^\)\]\}',?\n/;
 var $httpMinErr = minErr('$http');
-var $httpMinErrLegacyFn = function(method) {
-  return function() {
-    throw $httpMinErr('legacy', 'The method `{0}` on the promise returned from `$http` has been disabled.', method);
-  };
-};
 
 function serializeValue(v) {
   if (isObject(v)) {
@@ -346,30 +341,6 @@ function $HttpProvider() {
     return useApplyAsync;
   };
 
-  var useLegacyPromise = true;
-  /**
-   * @ngdoc method
-   * @name $httpProvider#useLegacyPromiseExtensions
-   * @description
-   *
-   * Configure `$http` service to return promises without the shorthand methods `success` and `error`.
-   * This should be used to make sure that applications work without these methods.
-   *
-   * Defaults to true. If no value is specified, returns the current configured value.
-   *
-   * @param {boolean=} value If true, `$http` will return a promise with the deprecated legacy `success` and `error` methods.
-   *
-   * @returns {boolean|Object} If a value is specified, returns the $httpProvider for chaining.
-   *    otherwise, returns the current configured value.
-   **/
-  this.useLegacyPromiseExtensions = function(value) {
-    if (isDefined(value)) {
-      useLegacyPromise = !!value;
-      return this;
-    }
-    return useLegacyPromise;
-  };
-
   /**
    * @ngdoc property
    * @name $httpProvider#interceptors
@@ -503,14 +474,6 @@ function $HttpProvider() {
      * $httpBackend.flush();
      * ```
      *
-     * ## Deprecation Notice
-     * <div class="alert alert-danger">
-     *   The `$http` legacy promise methods `success` and `error` have been deprecated.
-     *   Use the standard `then` method instead.
-     *   If {@link $httpProvider#useLegacyPromiseExtensions `$httpProvider.useLegacyPromiseExtensions`} is set to
-     *   `false` then these methods will throw {@link $http:legacy `$http/legacy`} error.
-     * </div>
-     *
      * ## Setting HTTP Headers
      *
      * The $http service will automatically add certain HTTP headers to all requests. These defaults
@@ -1000,29 +963,6 @@ function $HttpProvider() {
       promise = chainInterceptors(promise, responseInterceptors);
       promise = promise.finally(completeOutstandingRequest);
 
-      if (useLegacyPromise) {
-        promise.success = function(fn) {
-          assertArgFn(fn, 'fn');
-
-          promise.then(function(response) {
-            fn(response.data, response.status, response.headers, config);
-          });
-          return promise;
-        };
-
-        promise.error = function(fn) {
-          assertArgFn(fn, 'fn');
-
-          promise.then(null, function(response) {
-            fn(response.data, response.status, response.headers, config);
-          });
-          return promise;
-        };
-      } else {
-        promise.success = $httpMinErrLegacyFn('success');
-        promise.error = $httpMinErrLegacyFn('error');
-      }
-
       return promise;
 
 

src/ng/sce.js

@@ -612,8 +612,8 @@ function $SceDelegateProvider() {
  *     .controller('AppController', ['$http', '$templateCache', '$sce',
  *       function AppController($http, $templateCache, $sce) {
  *         var self = this;
- *         $http.get('test_data.json', {cache: $templateCache}).success(function(userComments) {
- *           self.userComments = userComments;
+ *         $http.get('test_data.json', {cache: $templateCache}).then(function(response) {
+ *           self.userComments = response.data;
  *         });
  *         self.explicitlyTrustedHtml = $sce.trustAsHtml(
  *             '<span onmouseover="this.textContent=&quot;Explicitly trusted HTML bypasses ' +