[fuchsia] Plumb content scaling override from Cast app config.

Adds a new field "force_content_dimensions" to the Cast
ApplicationConfig table. If the field is set, then the value is
passed to Frame::ForceContentDimensions() on application startup.

Bug: b/144361044,b/144725868
Change-Id: I895071e8236aaf0e55435b0c1ea5e6eef8008e46
Reviewed-on: https://chromium-review.googlesource.com/c/chromium/src/+/2029259
Commit-Queue: Kevin Marshall <kmarshall@chromium.org>
Reviewed-by: David Dorwin <ddorwin@chromium.org>
Reviewed-by: Wez <wez@chromium.org>
Cr-Commit-Position: refs/heads/master@{#737427}

fuchsia/fidl/cast/application_config.fidl

@@ -4,6 +4,7 @@
 
 library chromium.cast;
 
+using fuchsia.ui.gfx;
 using fuchsia.web;
 
 /// Describes the configuration under which a Cast application should run.
@@ -31,6 +32,9 @@ table ApplicationConfig {
 
   /// The URL of the agent to handle this application.
   7: string agent_url;
+
+  /// Simulates a different resolution for rendering.
+  8: fuchsia.ui.gfx.vec2 force_content_dimensions;
 };
 
 /// Service interface for working with application configurations.

fuchsia/runners/BUILD.gn

@@ -39,6 +39,7 @@ source_set("common") {
     "//fuchsia/base",
     "//fuchsia/base:modular",
     "//third_party/fuchsia-sdk/sdk:fuchsia-ui-app",
+    "//ui/gfx/geometry",
     "//url",
   ]
   public_deps = [

fuchsia/runners/cast/cast_component.cc

@@ -76,6 +76,11 @@ void CastComponent::StartComponent() {
                      kBindingsFailureExitCode,
                      fuchsia::sys::TerminationReason::INTERNAL_ERROR));
 
+  if (application_config_.has_force_content_dimensions()) {
+    frame()->ForceContentDimensions(std::make_unique<fuchsia::ui::gfx::vec2>(
+        application_config_.force_content_dimensions()));
+  }
+
   application_controller_ = std::make_unique<ApplicationControllerImpl>(
       frame(), agent_manager_->ConnectToAgentService<
                    chromium::cast::ApplicationControllerReceiver>(