Move InspectorFrontendHostAPI to externs

This was an interface that was already treated as an extern, but was not
explicitly in the externs.js file.

Bug: 1006759
Change-Id: I95301c059cc1213931498788cff553f955abb646
Reviewed-on: https://chromium-review.googlesource.com/c/chromium/src/+/1829098
Commit-Queue: Tim Van der Lippe <tvanderlippe@chromium.org>
Reviewed-by: Yang Guo <yangguo@chromium.org>
Cr-Original-Commit-Position: refs/heads/master@{#700724}
Cr-Mirrored-From: https://chromium.googlesource.com/chromium/src
Cr-Mirrored-Commit: c6c1bf57acb1c9ed7304674e7d5df51122cb22b1
diff --git a/scripts/compile_frontend.py b/scripts/compile_frontend.py
index 0f251eb..a15c1bc 100755
--- a/scripts/compile_frontend.py
+++ b/scripts/compile_frontend.py
@@ -358,9 +358,7 @@
 
     devtools_js_compile_command = closure_compiler_command + [
         '--externs',
-        to_platform_path(GLOBAL_EXTERNS_FILE), '--externs',
-        to_platform_path(path.join(DEVTOOLS_FRONTEND_PATH, 'host', 'InspectorFrontendHostAPI.js')),
-        '--jscomp_off=externsValidation', '--js',
+        to_platform_path(GLOBAL_EXTERNS_FILE), '--jscomp_off=externsValidation', '--js',
         to_platform_path(path.join(DEVTOOLS_FRONTEND_PATH, 'devtools_compatibility.js'))
     ]
     devtools_js_compile_proc = popen(devtools_js_compile_command)