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

content/app/content_main_runner.cc

Index: content/app/content_main_runner.cc
diff --git a/content/app/content_main_runner.cc b/content/app/content_main_runner.cc
index 279536b09b983deec9ae5f22856e5c0bbb72f83a..5e137aa0481ecba7b43049ae887ac1ede6428ad6 100644
--- a/content/app/content_main_runner.cc
+++ b/content/app/content_main_runner.cc
@@ -51,6 +51,10 @@
 #include "ui/base/ui_base_paths.h"
 #include "ui/base/ui_base_switches.h"
 
+#if defined(OS_ANDROID)
+#include "base/android/apk_assets.h"
+#endif
+
 #ifdef V8_USE_EXTERNAL_STARTUP_DATA
 #include "gin/v8_initializer.h"
 #endif
@@ -711,7 +715,16 @@ class ContentMainRunnerImpl : public ContentMainRunner {
 
 #if defined(V8_USE_EXTERNAL_STARTUP_DATA)
 #if defined(OS_POSIX) && !defined(OS_MACOSX)
-#if !defined(OS_ANDROID)
+#if defined(OS_ANDROID)
+    // The fds are already mapped in the case of Android WebView.

[rmcilroy, 2015/05/26 09:15:14]

Webview? Please update the comment.

Also, where have you added the code to do this pre-mapping? On Android Webview
this is done with AwAssets::RegisterAssetWithGlobalDescriptors [1], but I don't
see you doing anything similar here.

[1]
https://cs.corp.google.com/#clankium/src/android_webview/lib/main/aw_main_del...

+    if (g_fds->MaybeGet(kV8NativesDataDescriptor) == -1) {

[rmcilroy, 2015/05/26 09:15:14]

Please use the switches::kV8NativesPassedByFD and 
switches::kV8SnapshotPassedByFD and reuse the code below (you will need to
ensure you set the switches correctly). Otherwise this will cause issues with
Erik's on-demand snapshot generation where the kSnapshotFileName might not be
already mapped when the renderer starts depending on whether it has been
generated yet or not.

+      // Map V8 data from within .apk.
+      CHECK(base::android::RegisterApkAssetWithGlobalDescriptors(
+         kV8NativesDataDescriptor, gin::V8Initializer::kNativesFileName));
+      CHECK(base::android::RegisterApkAssetWithGlobalDescriptors(
+         kV8SnapshotDataDescriptor, gin::V8Initializer::kSnapshotFileName));
+    }
+#else
     // kV8NativesDataDescriptor and kV8SnapshotDataDescriptor could be shared
     // with child processes via file descriptors. On Android they are set in
     // ChildProcessService::InternalInitChildProcess, otherwise set them here.
@@ -725,7 +738,7 @@ class ContentMainRunnerImpl : public ContentMainRunner {
           kV8SnapshotDataDescriptor,
           kV8SnapshotDataDescriptor + base::GlobalDescriptors::kBaseDescriptor);
     }
-#endif  // !OS_ANDROID
+#endif  // OS_ANDROID
     int v8_natives_fd = g_fds->MaybeGet(kV8NativesDataDescriptor);
     int v8_snapshot_fd = g_fds->MaybeGet(kV8SnapshotDataDescriptor);
     if (v8_natives_fd != -1 && v8_snapshot_fd != -1) {