terminal: make XtermTerminal support tmux integration

Bug: b/236205389
Change-Id: I05572d59ac03d144ffcdf91cee862b783687248b
Reviewed-on: https://chromium-review.googlesource.com/c/apps/libapps/+/3944190
Tested-by: kokoro <noreply+kokoro@google.com>
Reviewed-by: Joel Hockey <joelhockey@chromium.org>
diff --git a/terminal/js/terminal_emulator_tests.js b/terminal/js/terminal_emulator_tests.js
index 7949af0..3c2d980 100644
--- a/terminal/js/terminal_emulator_tests.js
+++ b/terminal/js/terminal_emulator_tests.js
@@ -20,16 +20,11 @@
           parser: {
             registerOscHandler: () => {},
           },
-          _core: {
-            _renderService: {
-              dimensions: {
-                actualCellWidth: 10.5,
-                actualCellHeight: 20.5,
-              },
-            },
-          },
         }),
         fontManager: new MockObject(),
+        xtermInternal: new MockObject({
+          getActualCellDimensions: () => ({width: 9, height: 22}),
+        }),
       };
       const testParams = {};
       for (const prop in this.mocks) {