Set logger for loaded shared lib.

This will help IME service show logs better from loaded ime decoder.

TEST=Betty with new built DSO.
BUG=b/162375823

Change-Id: I9a3fa61078dfeae5a029b912c339cd80bc724a8a
Reviewed-on: https://chromium-review.googlesource.com/c/chromium/src/+/2497352
Commit-Queue: Leo Zhang <googleo@chromium.org>
Reviewed-by: Keith Lee <keithlee@chromium.org>
Cr-Commit-Position: refs/heads/master@{#821034}

chromeos/services/ime/ime_decoder.cc

@@ -28,6 +28,23 @@ base::FilePath GetImeDecoderLibPath() {
   return lib_path;
 }
 
+// Simple bridge between logging in the loaded shared library and logging in
+// Chrome.
+void ImeLoggerBridge(int severity, const char* message) {
+  switch (severity) {
+    case logging::LOG_INFO:
+      // TODO(b/162375823): VLOG_IF(INFO, is_debug_version).
+      break;
+    case logging::LOG_WARNING:
+      LOG(WARNING) << message;
+      break;
+    case logging::LOG_ERROR:
+      LOG(ERROR) << message;
+      break;
+    default:
+      break;
+  }
+}
 }  // namespace
 
 ImeDecoder::ImeDecoder() : status_(Status::kUninitialized) {
@@ -55,6 +72,16 @@ ImeDecoder::ImeDecoder() : status_(Status::kUninitialized) {
     return;
   }
 
+  ImeEngineLoggerSetterFn loggerSetter =
+      reinterpret_cast<ImeEngineLoggerSetterFn>(
+          library.GetFunctionPointer("SetImeEngineLogger"));
+  if (loggerSetter) {
+    loggerSetter(ImeLoggerBridge);
+  } else {
+    // Not a blocking issue yet.
+    LOG(ERROR) << "Failed to load SetImeEngineLogger function.";
+  }
+
   library_ = std::move(library);
   status_ = Status::kSuccess;
 }

chromeos/services/ime/public/cpp/shared_lib/interfaces.h

@@ -71,6 +71,9 @@ typedef void (*SimpleDownloadCallback)(int status_code, const char* file_path);
 // A function pointer of a sequenced task.
 typedef void (*ImeSequencedTask)(int task_id);
 
+// A logger function pointer from chrome.
+typedef void (*ChromeLoggerFunc)(int severity, const char* message);
+
 // Based on RequestPriority defined at
 // https://cs.chromium.org/chromium/src/net/base/request_priority.h?rcl=f9c935b73381772d508eebba1e216c437139d475
 enum DownloadPriority {
@@ -246,6 +249,9 @@ class ImeEngineMainEntry {
 // Returns an instance of ImeEngineMainEntry from the IME shared library.
 typedef ImeEngineMainEntry* (*ImeMainEntryCreateFn)(ImeCrosPlatform*);
 
+// For use when bridging logs logged in IME shared library to Chrome logging.
+typedef void (*ImeEngineLoggerSetterFn)(ChromeLoggerFunc);
+
 // Defined name of ImeMainEntryCreateFn exported from shared library.
 #define IME_MAIN_ENTRY_CREATE_FN_NAME "CreateImeMainEntry"