Load v8 snapshots directly from APK (and store them uncompressed)

gin/v8_initializer.cc

Index: gin/v8_initializer.cc
diff --git a/gin/v8_initializer.cc b/gin/v8_initializer.cc
index 1e1bd8dc6e865d10b73a4c68d064e271a5bdcfc0..2146c3fcbb65074e8d60df3f1abc6bdabebae090 100644
--- a/gin/v8_initializer.cc
+++ b/gin/v8_initializer.cc
@@ -17,6 +17,9 @@
 #include "crypto/sha2.h"
 
 #if defined(V8_USE_EXTERNAL_STARTUP_DATA)
+#if defined(OS_ANDROID)
+#include "base/android/apk_assets.h"
+#endif
 #if defined(OS_MACOSX)
 #include "base/mac/foundation_util.h"
 #endif  // OS_MACOSX
@@ -35,25 +38,24 @@ base::File* g_snapshot_file = nullptr;
 base::MemoryMappedFile::Region g_natives_region;
 base::MemoryMappedFile::Region g_snapshot_region;
 
-#if !defined(OS_MACOSX)
+#if !defined(OS_MACOSX) && !defined(OS_ANDROID)
 const int kV8SnapshotBasePathKey =
-#if defined(OS_ANDROID)
-    base::DIR_ANDROID_APP_DATA;
-#elif defined(OS_POSIX)
+#if defined(OS_POSIX)
     base::DIR_EXE;
 #elif defined(OS_WIN)
     base::DIR_MODULE;
-#endif  // OS_ANDROID
-#endif  // !OS_MACOSX
+#endif  // defined(OS_POSIX)
+#endif  // !defined(OS_MACOSX) && !defined(OS_ANDROID)
 
+#if defined(OS_ANDROID)
+const char kNativesFileName[] = "assets/natives_blob.bin";
+const char kSnapshotFileName[] = "assets/snapshot_blob.bin";

[rmcilroy, 2015/06/15 10:21:02]

this is effective the file path (within the APK) not the filename, right? I
think it would make more sense to have an #ifdef ANDROID in GetV8FilePath which
returns this. Also it might be worth just moving kV8SnapshotBasePathKey in there
(under the #if !defined(OS_MACOSX)) too since it's the only place this is used.

[agrieve, 2015/06/15 14:22:04]

Done.

+#else
 const char kNativesFileName[] = "natives_blob.bin";
 const char kSnapshotFileName[] = "snapshot_blob.bin";
+#endif  // defined(OS_ANDROID)
 
-// Constants for snapshot loading retries taken from:
-//   https://support.microsoft.com/en-us/kb/316609.
-const int kMaxOpenAttempts = 5;
-const int kOpenRetryDelayMillis = 250;
-
+#if !defined(OS_ANDROID)
 void GetV8FilePath(const char* file_name, base::FilePath* path_out) {
 #if !defined(OS_MACOSX)
   base::FilePath data_path;
@@ -68,6 +70,7 @@ void GetV8FilePath(const char* file_name, base::FilePath* path_out) {
 #endif  // !defined(OS_MACOSX)
   DCHECK(!path_out->empty());
 }
+#endif  // !defined(OS_ANDROID)
 
 static bool MapV8File(base::File file,
                       base::MemoryMappedFile::Region region,
@@ -86,9 +89,6 @@ static bool MapV8File(base::File file,
 
 base::File OpenV8File(const char* file_name,
                       base::MemoryMappedFile::Region* region_out) {
-  // Re-try logic here is motivated by http://crbug.com/479537
-  // for A/V on Windows (https://support.microsoft.com/en-us/kb/316609).
-
   // These match tools/metrics/histograms.xml
   enum OpenV8FileResult {
     OPENED = 0,
@@ -97,6 +97,15 @@ base::File OpenV8File(const char* file_name,
     FAILED_OTHER,
     MAX_VALUE
   };
+#if defined(OS_ANDROID)
+  base::File file(base::android::OpenApkAsset(file_name, region_out));
+  OpenV8FileResult result = file.IsValid() ? OpenV8FileResult::OPENED
+                                           : OpenV8FileResult::FAILED_OTHER;
+#else
+  // Re-try logic here is motivated by http://crbug.com/479537
+  // for A/V on Windows (https://support.microsoft.com/en-us/kb/316609).
+  const int kMaxOpenAttempts = 5;
+  const int kOpenRetryDelayMillis = 250;
 
   base::FilePath path;
   GetV8FilePath(file_name, &path);
@@ -123,6 +132,7 @@ base::File OpenV8File(const char* file_name,
           base::TimeDelta::FromMilliseconds(kOpenRetryDelayMillis));
     }
   }
+#endif  // defined(OS_ANDROID)
 
   UMA_HISTOGRAM_ENUMERATION("V8.Initializer.OpenV8File.Result",
                             result,