Make the Windows multi_dll build work in GN

chrome/common/extensions/api/BUILD.gn

Index: chrome/common/extensions/api/BUILD.gn
diff --git a/chrome/common/extensions/api/BUILD.gn b/chrome/common/extensions/api/BUILD.gn
index 2b538f923a924413a439c282d0690106f8f03718..d63f49033f85aa5414da8b0f7b946dd90f716ff0 100644
--- a/chrome/common/extensions/api/BUILD.gn
+++ b/chrome/common/extensions/api/BUILD.gn
@@ -39,4 +39,11 @@ json_schema_api("api_registration") {
     # deps += [ "<(DEPTH)/chrome/chrome.gyp:drive_proto" ]  TODO(GYP)
   }
   deps += schema_dependencies
+
+  # This must be a static library because the generated schemas have
+  # dependencies into both the browser and child processes, and this won't link
+  # in the multi DLL build. In the child DLL, only some files are needed, and
+  # these have no dependencies into the browser, so a static library solves the
+  # problem.
+  generate_static_library = true
 }