Bug 1647972 - Add a new PlatformOverride field onto BrowsingContext r=smaug

Differential Revision: https://phabricator.services.mozilla.com/D81285

docshell/base/BrowsingContext.cpp

@@ -2037,6 +2037,21 @@ void BrowsingContext::DidSet(FieldIndex<IDX_UserAgentOverride>) {
   });
 }
 
+void BrowsingContext::SetCustomPlatform(const nsAString& aPlatform) {
+  Top()->SetPlatformOverride(aPlatform);
+}
+
+void BrowsingContext::DidSet(FieldIndex<IDX_PlatformOverride>) {
+  MOZ_ASSERT(IsTop());
+
+  PreOrderWalk([&](BrowsingContext* aContext) {
+    nsIDocShell* shell = aContext->GetDocShell();
+    if (shell) {
+      shell->ClearCachedPlatform();
+    }
+  });
+}
+
 bool BrowsingContext::CheckOnlyOwningProcessCanSet(ContentParent* aSource) {
   if (aSource) {
     MOZ_ASSERT(XRE_IsParentProcess());
@@ -2148,6 +2163,16 @@ bool BrowsingContext::CanSet(FieldIndex<IDX_UserAgentOverride>,
   return CheckOnlyOwningProcessCanSet(aSource);
 }
 
+bool BrowsingContext::CanSet(FieldIndex<IDX_PlatformOverride>,
+                             const nsString& aPlatform,
+                             ContentParent* aSource) {
+  if (!IsTop()) {
+    return false;
+  }
+
+  return CheckOnlyOwningProcessCanSet(aSource);
+}
+
 bool BrowsingContext::CheckOnlyEmbedderCanSet(ContentParent* aSource) {
   if (aSource) {
     // Set by a content process, verify that it's this BC's embedder.

docshell/base/BrowsingContext.h

@@ -148,7 +148,8 @@ class WindowProxyHolder;
    * This is only ever set to true on the top BC, so consumers need to get   \
    * the value from the top BC! */                                           \
   FIELD(HasSessionHistory, bool)                                             \
-  FIELD(UseErrorPages, bool)
+  FIELD(UseErrorPages, bool)                                                 \
+  FIELD(PlatformOverride, nsString)
 
 // BrowsingContext, in this context, is the cross process replicated
 // environment in which information about documents is stored. In
@@ -557,6 +558,11 @@ class BrowsingContext : public nsILoadContext, public nsWrapperCache {
   }
   void SetCustomUserAgent(const nsAString& aUserAgent);
 
+  void GetCustomPlatform(nsAString& aPlatform) {
+    aPlatform = Top()->GetPlatformOverride();
+  }
+  void SetCustomPlatform(const nsAString& aPlatform);
+
   JSObject* WrapObject(JSContext* aCx);
 
   static JSObject* ReadStructuredClone(JSContext* aCx,
@@ -750,6 +756,10 @@ class BrowsingContext : public nsILoadContext, public nsWrapperCache {
 
   void DidSet(FieldIndex<IDX_AncestorLoading>);
 
+  void DidSet(FieldIndex<IDX_PlatformOverride>);
+  bool CanSet(FieldIndex<IDX_PlatformOverride>,
+              const nsString& aPlatformOverride, ContentParent* aSource);
+
   void DidSet(FieldIndex<IDX_UserAgentOverride>);
   bool CanSet(FieldIndex<IDX_UserAgentOverride>, const nsString& aUserAgent,
               ContentParent* aSource);

docshell/base/nsDocShell.cpp

@@ -2148,6 +2148,20 @@ nsDocShell::SetCustomUserAgent(const nsAString& aCustomUserAgent) {
   return NS_OK;
 }
 
+NS_IMETHODIMP
+nsDocShell::ClearCachedPlatform() {
+  RefPtr<nsGlobalWindowInner> win =
+      mScriptGlobal ? mScriptGlobal->GetCurrentInnerWindowInternal() : nullptr;
+  if (win) {
+    Navigator* navigator = win->Navigator();
+    if (navigator) {
+      navigator->ClearPlatformCache();
+    }
+  }
+
+  return NS_OK;
+}
+
 NS_IMETHODIMP
 nsDocShell::ClearCachedUserAgent() {
   RefPtr<nsGlobalWindowInner> win =

docshell/base/nsIDocShell.idl

@@ -395,6 +395,8 @@ interface nsIDocShell : nsIDocShellTreeItem
 
   void clearCachedUserAgent();
 
+  void clearCachedPlatform();
+
   /* Track whether we're currently restoring a document presentation. */
   readonly attribute boolean restoringDocument;
 

docshell/test/browser/browser.ini

@@ -133,6 +133,7 @@ skip-if = (os == 'win' && !debug) # bug 1300351
 [browser_overlink.js]
 support-files =
   overlink_test.html
+[browser_platform_emulation.js]
 [browser_search_notification.js]
 [browser_tab_touch_events.js]
 [browser_timelineMarkers-01.js]

docshell/test/browser/browser_platform_emulation.js

@@ -0,0 +1,69 @@
+/* Any copyright is dedicated to the Public Domain.
+   http://creativecommons.org/publicdomain/zero/1.0/ */
+
+"use strict";
+
+const URL = "data:text/html;charset=utf-8,<iframe id='test-iframe'></iframe>";
+
+async function contentTaskNoOverride() {
+  let docshell = docShell;
+  is(
+    docshell.browsingContext.customPlatform,
+    "",
+    "There should initially be no customPlatform"
+  );
+}
+
+async function contentTaskOverride() {
+  let docshell = docShell;
+  is(
+    docshell.browsingContext.customPlatform,
+    "foo",
+    "The platform should be changed to foo"
+  );
+
+  is(
+    content.navigator.platform,
+    "foo",
+    "The platform should be changed to foo"
+  );
+
+  let frameWin = content.document.querySelector("#test-iframe").contentWindow;
+  is(
+    frameWin.navigator.platform,
+    "foo",
+    "The platform should be passed on to frames."
+  );
+
+  let newFrame = content.document.createElement("iframe");
+  content.document.body.appendChild(newFrame);
+
+  let newFrameWin = newFrame.contentWindow;
+  is(
+    newFrameWin.navigator.platform,
+    "foo",
+    "Newly created frames should use the new platform"
+  );
+
+  newFrameWin.location.reload();
+  await ContentTaskUtils.waitForEvent(newFrameWin, "load");
+
+  is(
+    newFrameWin.navigator.platform,
+    "foo",
+    "New platform should persist across reloads"
+  );
+}
+
+add_task(async function() {
+  await BrowserTestUtils.withNewTab({ gBrowser, url: URL }, async function(
+    browser
+  ) {
+    await SpecialPowers.spawn(browser, [], contentTaskNoOverride);
+
+    let browsingContext = BrowserTestUtils.getBrowsingContextFrom(browser);
+    browsingContext.customPlatform = "foo";
+
+    await SpecialPowers.spawn(browser, [], contentTaskOverride);
+  });
+});

dom/base/Navigator.cpp

@@ -400,6 +400,19 @@ void Navigator::GetLanguages(nsTArray<nsString>& aLanguages) {
 
 void Navigator::GetPlatform(nsAString& aPlatform, CallerType aCallerType,
                             ErrorResult& aRv) const {
+  if (mWindow) {
+    BrowsingContext* bc = mWindow->GetBrowsingContext();
+    nsString customPlatform;
+    if (bc) {
+      bc->GetCustomPlatform(customPlatform);
+
+      if (!customPlatform.IsEmpty()) {
+        aPlatform = customPlatform;
+        return;
+      }
+    }
+  }
+
   nsCOMPtr<Document> doc = mWindow->GetExtantDoc();
 
   nsresult rv = GetPlatform(
@@ -1769,6 +1782,10 @@ already_AddRefed<nsPIDOMWindowInner> Navigator::GetWindowFromGlobal(
   return win.forget();
 }
 
+void Navigator::ClearPlatformCache() {
+  Navigator_Binding::ClearCachedPlatformValue(this);
+}
+
 nsresult Navigator::GetPlatform(nsAString& aPlatform,
                                 nsIPrincipal* aCallerPrincipal,
                                 bool aUsePrefOverriddenValue) {

dom/base/Navigator.h

@@ -148,6 +148,10 @@ class Navigator final : public nsISupports, public nsWrapperCache {
                                nsIPrincipal* aCallerPrincipal,
                                bool aIsCallerChrome, nsAString& aUserAgent);
 
+  // Clears the platform cache by calling:
+  // Navigator_Binding::ClearCachedPlatformValue(this);
+  void ClearPlatformCache();
+
   // Clears the user agent cache by calling:
   // Navigator_Binding::ClearCachedUserAgentValue(this);
   void ClearUserAgentCache();

dom/chrome-webidl/BrowsingContext.webidl

@@ -66,6 +66,8 @@ interface BrowsingContext {
 
   readonly attribute WindowContext? topWindowContext;
 
+  attribute [TreatNullAs=EmptyString] DOMString customPlatform;
+
   attribute [TreatNullAs=EmptyString] DOMString customUserAgent;
 
   /**

dom/webidl/Navigator.webidl

@@ -50,7 +50,7 @@ interface mixin NavigatorID {
   readonly attribute DOMString appName;
   [Constant, Cached, Throws, NeedsCallerType]
   readonly attribute DOMString appVersion;
-  [Constant, Cached, Throws, NeedsCallerType]
+  [Pure, Cached, Throws, NeedsCallerType]
   readonly attribute DOMString platform;
   [Pure, Cached, Throws, NeedsCallerType]
   readonly attribute DOMString userAgent;