Drive-by: IWYU (component_export.h)

This CL introduces no behavioral change. It was generated by issuing

```
for f in $(rg -l "COMPONENT_EXPORT" |
    xargs rg --files-without-match "component_export\.h" |
    rg "\.h$");
  do printf '\n\n%s\n' '#include "base/component_export.h"' >> "${f}";
done
```

under `ui/`, followed an embarrassing amount of vim-fiddling when I
realized that an `#include` at the very bottom of the file wasn't
handled by `git cl format`.

AX-Relnotes: n/a
Change-Id: I7a3e326ad8b1438a00aea667668da772b66c3a6e
Reviewed-on: https://chromium-review.googlesource.com/c/chromium/src/+/5999171
Commit-Queue: Kalvin Lee <[email protected]>
Reviewed-by: Colin Blundell <[email protected]>
Reviewed-by: Takashi Toyoshima <[email protected]>
Reviewed-by: Hidehiko Abe <[email protected]>
Cr-Commit-Position: refs/heads/main@{#1379516}
diff --git a/ui/linux/linux_ui_delegate_stub.h b/ui/linux/linux_ui_delegate_stub.h
index 92304cb..0711cee 100644
--- a/ui/linux/linux_ui_delegate_stub.h
+++ b/ui/linux/linux_ui_delegate_stub.h
@@ -5,6 +5,7 @@
 #ifndef UI_LINUX_LINUX_UI_DELEGATE_STUB_H_
 #define UI_LINUX_LINUX_UI_DELEGATE_STUB_H_
 
+#include "base/component_export.h"
 #include "ui/linux/linux_ui_delegate.h"
 
 namespace ui {