Rationalize and fix chromium android linker histogram recording.

base/android/library_loader/library_loader_hooks.cc

 // Copyright 2014 The Chromium Authors. All rights reserved.
 // Use of this source code is governed by a BSD-style license that can be
 // found in the LICENSE file.
 
 #include "base/android/library_loader/library_loader_hooks.h"
 
 #include "base/android/command_line_android.h"
 #include "base/android/jni_string.h"
 #include "base/at_exit.h"
 #include "base/metrics/histogram.h"
 #include "jni/LibraryLoader_jni.h"
 
 namespace base {
 namespace android {
 
 namespace {
 
 base::AtExitManager* g_at_exit_manager = NULL;
 const char* g_library_version_number = "";
 LibraryLoadedHook* g_registration_callback = NULL;
 
+bool g_has_renderer_histogram = false;
+bool g_load_renderer_at_fixed_address_failed = false;
+
 } // namespace
 
+void RegisterChromiumAndroidLinkerRendererHistogram(

[rmcilroy, 2014/10/01 12:14:42]

nit - please move down below LibraryLoaded()

[simonb (inactive), 2014/10/02 15:15:30]

Acknowledged.

+    bool load_at_fixed_address_failed) {
+  g_has_renderer_histogram = true;
+  g_load_renderer_at_fixed_address_failed = load_at_fixed_address_failed;
+}
+
+void RecordChromiumAndroidLinkerRendererHistogram() {
+  if (g_has_renderer_histogram) {
+    UMA_HISTOGRAM_BOOLEAN(
+        "ChromiumAndroidLinker.LoadedRendererAtFixedAddressFailed",
+        g_load_renderer_at_fixed_address_failed);
+    g_has_renderer_histogram = false;

[rmcilroy, 2014/10/01 12:14:42]

Maybe call the boolean g_renderer_histogram_registered_but_not_recorded since
you are also using it to ensure you don't send the UMA more than once.

[simonb (inactive), 2014/10/02 15:15:30]

Acknowledged.  The separate boolean disappeared in a rewrite.

+  }
+}
+
 void SetLibraryLoadedHook(LibraryLoadedHook* func) {
   g_registration_callback = func;
 }
 
 static void InitCommandLine(JNIEnv* env, jclass clazz,
                             jobjectArray init_command_line) {
   InitNativeCommandLineFromJavaArray(env, init_command_line);
 }
 
 static jboolean LibraryLoaded(JNIEnv* env, jclass clazz) {
-  if(g_registration_callback == NULL) {
+  if (g_registration_callback == NULL) {
     return true;
   }
   return g_registration_callback(env, clazz);
 }
 
-static void RecordChromiumAndroidLinkerHistogram(
+static void RecordChromiumAndroidLinkerBrowserHistograms(
     JNIEnv* env,
     jclass clazz,
-    jboolean loaded_at_fixed_address_failed,
-    jboolean is_low_memory_device) {
-  UMA_HISTOGRAM_BOOLEAN("ChromiumAndroidLinker.LoadedAtFixedAddressFailed",
-                        loaded_at_fixed_address_failed);
-  UMA_HISTOGRAM_BOOLEAN("ChromiumAndroidLinker.IsLowMemoryDevice",
-                        is_low_memory_device);
+    jboolean is_using_browser_shared_relros,
+    jboolean loaded_browser_at_fixed_address_failed) {
+  UMA_HISTOGRAM_BOOLEAN(
+      "ChromiumAndroidLinker.IsUsingBrowserSharedRelros",
+      is_using_browser_shared_relros);
+  UMA_HISTOGRAM_BOOLEAN(
+      "ChromiumAndroidLinker.LoadedBrowserAtFixedAddressFailed",
+      loaded_browser_at_fixed_address_failed);
 }
 
 void LibraryLoaderExitHook() {
   if (g_at_exit_manager) {
     delete g_at_exit_manager;
     g_at_exit_manager = NULL;
   }
 }
 
 bool RegisterLibraryLoaderEntryHook(JNIEnv* env) {
@@ skipping 10 matching lines @@
 jstring GetVersionNumber(JNIEnv* env, jclass clazz) {
   return ConvertUTF8ToJavaString(env, g_library_version_number).Release();
 }
 
 static void RecordNativeLibraryHack(JNIEnv*, jclass, jboolean usedHack) {
   UMA_HISTOGRAM_BOOLEAN("LibraryLoader.NativeLibraryHack", usedHack);
 }
 
 }  // namespace android
 }  // namespace base