Add UMA for testing whether device supports memory mapping APK files with executable permissions.

base/android/java/src/org/chromium/base/library_loader/LibraryLoader.java

Index: base/android/java/src/org/chromium/base/library_loader/LibraryLoader.java
diff --git a/base/android/java/src/org/chromium/base/library_loader/LibraryLoader.java b/base/android/java/src/org/chromium/base/library_loader/LibraryLoader.java
index fc6d46fb99771f26383d788fbe41a2254caafc76..155cbffe00af938a6b64cf1421283cae6b5aca5a 100644
--- a/base/android/java/src/org/chromium/base/library_loader/LibraryLoader.java
+++ b/base/android/java/src/org/chromium/base/library_loader/LibraryLoader.java
@@ -50,6 +50,10 @@ public class LibraryLoader {
     private static boolean sIsUsingBrowserSharedRelros = false;
     private static boolean sLoadAtFixedAddressFailed = false;
 
+    // One-way switch recording whether the device supports memory mapping
+    // APK files with executable permissions.

[rmcilroy, 2014/10/10 16:26:08]

add: Only used in the browser.

[petrcermak, 2014/10/10 17:13:23]

Done.

+    private static boolean sApkMemoryMappingSupported = false;

[rmcilroy, 2014/10/10 16:26:08]

Can we make this a bit more generic (in case we add other checks here) - e.g.,
sLibraryLoadFromApkSupported.  Also change the histogram.xml as such.

[petrcermak, 2014/10/10 17:13:24]

Done.

+
     // One-way switch becomes true if the system library loading failed,
     // and the right native library was found and loaded by the hack.
     // The flag is used to report UMA stats later.
@@ -160,6 +164,13 @@ public class LibraryLoader {
                     // Load libraries using the Chromium linker.
                     Linker.prepareLibraryLoad();
 
+                    // Check if the device supports memory mapping APK files with executable
+                    // permissions.

[rmcilroy, 2014/10/10 16:26:08]

nit - "Check if the device supports loading a library directly from the APK
file." 

[petrcermak, 2014/10/10 17:13:24]

Done.

+                    if (Linker.isInBrowserProcess()) {
+                        sApkMemoryMappingSupported = Linker.checkApkMemoryMappingSupport(
+                                context.getApplicationInfo().sourceDir);

[rmcilroy, 2014/10/10 16:26:07]

nit - pull out "context.getApplicationInfo().sourceDir" to a variable set above
and used both here and L177

[petrcermak, 2014/10/10 17:13:23]

Done.

+                    }
+
                     for (String library : NativeLibraries.LIBRARIES) {
                         String zipfile = null;
                         if (Linker.isInZipFile()) {
@@ -305,8 +316,10 @@ public class LibraryLoader {
     // onNativeInitializationComplete().
     private static void recordBrowserProcessHistogram() {
         if (Linker.isUsed()) {
+            assert Linker.isInBrowserProcess();
             nativeRecordChromiumAndroidLinkerBrowserHistogram(sIsUsingBrowserSharedRelros,
-                                                              sLoadAtFixedAddressFailed);
+                                                              sLoadAtFixedAddressFailed,
+                                                              sApkMemoryMappingSupported);
         }
     }
 
@@ -334,10 +347,12 @@ public class LibraryLoader {
 
     // Method called to record statistics about the Chromium linker operation for the main
     // browser process. Indicates whether the linker attempted relro sharing for the browser,
-    // and if it did, whether the library failed to load at a fixed address.
+    // and if it did, whether the library failed to load at a fixed address. Also records
+    // support for memory mapping APK files with executable permissions.
     private static native void nativeRecordChromiumAndroidLinkerBrowserHistogram(
             boolean isUsingBrowserSharedRelros,
-            boolean loadAtFixedAddressFailed);
+            boolean loadAtFixedAddressFailed,
+            boolean apkMemoryMappingSupported);
 
     // Method called to register (for later recording) statistics about the Chromium linker
     // operation for a renderer process. Indicates whether the linker attempted relro sharing,