Cleanup Android logger code (#1367)

Summary:
X-link: https://github.com/facebook/react-native/pull/39373

Pull Request resolved: https://github.com/facebook/yoga/pull/1367

Moves some messiness around conditionally using Android's logger to `Log.cpp`, isolated to within a single function.

Reviewed By: rshest

Differential Revision: D49131964

fbshipit-source-id: cdff8af1d4df6ae28f00eecfed1920c71eec24d0

yoga/debug/Log.cpp

@@ -7,6 +7,10 @@
 
 #include <yoga/debug/Log.h>
 
+#ifdef ANDROID
+#include <android/log.h>
+#endif
+
 namespace facebook::yoga {
 
 namespace {
@@ -62,4 +66,49 @@ void log(
   va_end(args);
 }
 
+YGLogger getDefaultLogger() {
+  return [](const YGConfigConstRef /*config*/,
+            const YGNodeConstRef /*node*/,
+            YGLogLevel level,
+            const char* format,
+            va_list args) -> int {
+#ifdef ANDROID
+    int androidLevel = YGLogLevelDebug;
+    switch (level) {
+      case YGLogLevelFatal:
+        androidLevel = ANDROID_LOG_FATAL;
+        break;
+      case YGLogLevelError:
+        androidLevel = ANDROID_LOG_ERROR;
+        break;
+      case YGLogLevelWarn:
+        androidLevel = ANDROID_LOG_WARN;
+        break;
+      case YGLogLevelInfo:
+        androidLevel = ANDROID_LOG_INFO;
+        break;
+      case YGLogLevelDebug:
+        androidLevel = ANDROID_LOG_DEBUG;
+        break;
+      case YGLogLevelVerbose:
+        androidLevel = ANDROID_LOG_VERBOSE;
+        break;
+    }
+    return __android_log_vprint(androidLevel, "yoga", format, args);
+#else
+    switch (level) {
+      case YGLogLevelError:
+      case YGLogLevelFatal:
+        return vfprintf(stderr, format, args);
+      case YGLogLevelWarn:
+      case YGLogLevelInfo:
+      case YGLogLevelDebug:
+      case YGLogLevelVerbose:
+      default:
+        return vprintf(format, args);
+    }
+#endif
+  };
+}
+
 } // namespace facebook::yoga

yoga/debug/Log.h

@@ -7,6 +7,8 @@
 
 #pragma once
 
+#include <yoga/Yoga.h>
+
 #include <yoga/YGEnums.h>
 #include <yoga/node/Node.h>
 #include <yoga/config/Config.h>
@@ -29,4 +31,6 @@ void log(
     const char* format,
     ...) noexcept;
 
+YGLogger getDefaultLogger();
+
 } // namespace facebook::yoga