Record the return value of NativeLibraryPreloader.loadLibrary in UMA

base/android/library_loader/library_loader_hooks.cc

Index: base/android/library_loader/library_loader_hooks.cc
diff --git a/base/android/library_loader/library_loader_hooks.cc b/base/android/library_loader/library_loader_hooks.cc
index bbc99352f6d8211146574ca3025328de0bfcbbaf..578eaa8be11b1abc58df948aaaa344364180e116 100644
--- a/base/android/library_loader/library_loader_hooks.cc
+++ b/base/android/library_loader/library_loader_hooks.cc
@@ -10,6 +10,7 @@
 #include "base/android/library_loader/library_prefetcher.h"
 #include "base/at_exit.h"
 #include "base/metrics/histogram.h"
+#include "base/metrics/sparse_histogram.h"
 #include "jni/LibraryLoader_jni.h"
 
 namespace base {
@@ -48,6 +49,12 @@ enum BrowserHistogramCode {
 
 RendererHistogramCode g_renderer_histogram_code = NO_PENDING_HISTOGRAM_CODE;
 
+// Indicate whether g_library_preloader_renderer_histogram_code is valid
+bool g_library_preloader_renderer_histogram_code_registered = false;
+
+// The return value of NativeLibraryPreloader.loadLibrary() in child processes.
+int g_library_preloader_renderer_histogram_code = 0;
+
 // The amount of time, in milliseconds, that it took to load the shared
 // libraries in the renderer. Set in
 // RegisterChromiumAndroidLinkerRendererHistogram.
@@ -72,8 +79,8 @@ static void RegisterChromiumAndroidLinkerRendererHistogram(
   g_renderer_library_load_time_ms = library_load_time_ms;
 }
 
-void RecordChromiumAndroidLinkerRendererHistogram() {
-  if (g_renderer_histogram_code == NO_PENDING_HISTOGRAM_CODE)
+static void RecordChromiumAndroidLinkerRendererHistogram() {
+  if (g_renderer_histogram_code != NO_PENDING_HISTOGRAM_CODE)
     return;
   // Record and release the pending histogram value.
   UMA_HISTOGRAM_ENUMERATION("ChromiumAndroidLinker.RendererStates",
@@ -116,6 +123,36 @@ static void RecordChromiumAndroidLinkerBrowserHistogram(
                       base::TimeDelta::FromMilliseconds(library_load_time_ms));
 }
 
+static void RecordLibraryPreloaderBrowserHistogram(
+    JNIEnv* env,
+    const JavaParamRef<jobject>& jcaller,
+    jint status) {
+  UMA_HISTOGRAM_SPARSE_SLOWLY(
+      "ChromiumAndroidNativeLibraryPreloader.BrowserStates",
+      status);
+}
+
+static void RegisterLibraryPreloaderRendererHistogram(
+    JNIEnv* env,
+    const JavaParamRef<jobject>& jcaller,
+    jint status) {
+  g_library_preloader_renderer_histogram_code = status;
+  g_library_preloader_renderer_histogram_code_registered = true;
+}
+
+static void RecordLibraryPreloaderRendereHistogram() {
+  if (g_library_preloader_renderer_histogram_code_registered) {
+    UMA_HISTOGRAM_SPARSE_SLOWLY(
+        "ChromiumAndroidNativeLibraryPreloader.RendererStates",

[Alexei Svitkine (slow), 2016/05/26 14:56:29]

I suggest not adding a new histogram prefix unless you expect it will be used a
lot for new metrics.

So perhaps you can nest these under the existing Android.* prefix?

e.g. Android.NativeLibraryPreloader.RendererStates

Also, this is the result of loadLibrary(), right?

So maybe Android.NativeLibraryPreloader.Result.Browser and
Android.NativeLibraryPreloader.Result.Renderer?

The "Browser" and "Renderer" suffixes are a standard way on how to permute a
histogram in UMA and is supported via histogram_suffixes in histograms.xml.

[michaelbai, 2016/05/26 19:10:35]

Done.

+        g_library_preloader_renderer_histogram_code);
+  }
+}
+
+void RecordChromiumAndroidLibraryLoaderRendererHistogram() {
+  RecordChromiumAndroidLinkerRendererHistogram();
+  RecordLibraryPreloaderRendereHistogram();
+}
+
 void SetLibraryLoadedHook(LibraryLoadedHook* func) {
   g_registration_callback = func;
 }