refactor(platform-browser): Hoist functions to workaround optimization bug. (angular#32230)

Technically, function definitions can live anywhere because they are
hoisted. However, in this case Closure optimizations break when exported
function definitions are referred in another static object that is
exported.

The bad pattern is:
```
exports const obj = {f};
export function f() {...}
```

which turns to the following in Closure's module system:
```
goog.module('m');

exports.obj = {f};

function f() {...}
exports.f = f;
```

which badly optimizes to (note module objects are collapsed)
```
var b = a; var a = function() {...};  // now b is undefined.
```

This is an optimizer bug and should be fixed in Closure, but in the
meantime this change is a noop and will unblock other changes we want to
make.

PR Close angular#32230

Author: rkirov

packages/platform-browser/src/browser.ts

@@ -20,6 +20,21 @@ import {KeyEventsPlugin} from './dom/events/key_events';
 import {DomSharedStylesHost, SharedStylesHost} from './dom/shared_styles_host';
 import {DomSanitizer, DomSanitizerImpl} from './security/dom_sanitization_service';
 
+export function initDomAdapter() {
+  BrowserDomAdapter.makeCurrent();
+  BrowserGetTestability.init();
+}
+
+export function errorHandler(): ErrorHandler {
+  return new ErrorHandler();
+}
+
+export function _document(): any {
+  // Tell ivy about the global document
+  ɵsetDocument(document);
+  return document;
+}
+
 export const INTERNAL_BROWSER_PLATFORM_PROVIDERS: StaticProvider[] = [
   {provide: PLATFORM_ID, useValue: PLATFORM_BROWSER_ID},
   {provide: PLATFORM_INITIALIZER, useValue: initDomAdapter, multi: true},
@@ -47,21 +62,6 @@ export const BROWSER_SANITIZATION_PROVIDERS = BROWSER_SANITIZATION_PROVIDERS__PR
 export const platformBrowser: (extraProviders?: StaticProvider[]) => PlatformRef =
     createPlatformFactory(platformCore, 'browser', INTERNAL_BROWSER_PLATFORM_PROVIDERS);
 
-export function initDomAdapter() {
-  BrowserDomAdapter.makeCurrent();
-  BrowserGetTestability.init();
-}
-
-export function errorHandler(): ErrorHandler {
-  return new ErrorHandler();
-}
-
-export function _document(): any {
-  // Tell ivy about the global document
-  ɵsetDocument(document);
-  return document;
-}
-
 export const BROWSER_MODULE_PROVIDERS: StaticProvider[] = [
   BROWSER_SANITIZATION_PROVIDERS,
   {provide: INJECTOR_SCOPE, useValue: 'root'},