Auto merge of #11430 - asajeffrey:constellation-record-mozbrowser-parent-info, r=ConnorGBrewster

Record the frame type (IFrame or MozBrowserIFrame) in the pipeline.

Thank you for contributing to Servo! Please replace each `[ ]` by `[X]` when the step is complete, and replace `__` with appropriate data:
- [X] `./mach build -d` does not report any errors
- [X] `./mach test-tidy` does not report any errors
- [X] These changes do not require tests because this is a refactoring

Pull requests that do not address these steps are welcome, but they will require additional verification as part of the review process.

This is a first step towards supporting the notion of multiple top-level browsing contexts in Servo, by making the constellation aware of which content is loaded in a mozbrowser iframe.

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components/script_traits/lib.rs

@@ -41,7 +41,7 @@ use gfx_traits::Epoch;
 use gfx_traits::LayerId;
 use ipc_channel::ipc::{IpcReceiver, IpcSender};
 use libc::c_void;
-use msg::constellation_msg::{FrameId, Key, KeyModifiers, KeyState, LoadData};
+use msg::constellation_msg::{FrameId, FrameType, Key, KeyModifiers, KeyState, LoadData};
 use msg::constellation_msg::{NavigationDirection, PanicMsg, PipelineId};
 use msg::constellation_msg::{PipelineNamespaceId, SubpageId, WindowSizeData};
 use msg::constellation_msg::{WebDriverCommandMsg, WindowSizeType};
@@ -372,6 +372,8 @@ pub struct IFrameLoadInfo {
     pub sandbox: IFrameSandboxState,
     ///  Whether this iframe should be considered private
     pub is_private: bool,
+    /// Whether this iframe is a mozbrowser iframe
+    pub frame_type: FrameType,
 }
 
 // https://developer.mozilla.org/en-US/docs/Web/API/Using_the_Browser_API#Events