mmap V8 snapshot and ICU data file in the android_webview

This makes it possible to mmap the V8 snapshot and ICU data file
directly from the WebView APK.
Doing so makes it possible to remove the android_webview_telemetry_build
flag which in turns means we can build the WebView with the same
set of flags that Chrome on Android uses.

BUG=442338

Review URL: https://codereview.chromium.org/812393002

Cr-Commit-Position: refs/heads/master@{#310765}

2 files changed, 54 insertions, 11 deletions

diff --git a/base/posix/global_descriptors.cc b/base/posix/global_descriptors.cc
index bcca443..6c18783 100644
--- a/base/posix/global_descriptors.cc
+++ b/base/posix/global_descriptors.cc
@@ -11,6 +11,16 @@
 
 namespace base {
 
+GlobalDescriptors::Descriptor::Descriptor(Key key, int fd)
+    : key(key), fd(fd), region(base::MemoryMappedFile::Region::kWholeFile) {
+}
+
+GlobalDescriptors::Descriptor::Descriptor(Key key,
+                                          int fd,
+                                          base::MemoryMappedFile::Region region)
+    : key(key), fd(fd), region(region) {
+}
+
 // static
 GlobalDescriptors* GlobalDescriptors::GetInstance() {
   typedef Singleton<base::GlobalDescriptors,
@@ -30,23 +40,38 @@ int GlobalDescriptors::Get(Key key) const {
 int GlobalDescriptors::MaybeGet(Key key) const {
   for (Mapping::const_iterator
        i = descriptors_.begin(); i != descriptors_.end(); ++i) {
-    if (i->first == key)
-      return i->second;
+    if (i->key == key)
+      return i->fd;
   }
 
   return -1;
 }
 
 void GlobalDescriptors::Set(Key key, int fd) {
-  for (Mapping::iterator
-       i = descriptors_.begin(); i != descriptors_.end(); ++i) {
-    if (i->first == key) {
-      i->second = fd;
+  Set(key, fd, base::MemoryMappedFile::Region::kWholeFile);
+}
+
+void GlobalDescriptors::Set(Key key,
+                            int fd,
+                            base::MemoryMappedFile::Region region) {
+  for (auto& i : descriptors_) {
+    if (i.key == key) {
+      i.fd = fd;
+      i.region = region;
       return;
     }
   }
 
-  descriptors_.push_back(std::make_pair(key, fd));
+  descriptors_.push_back(Descriptor(key, fd, region));
+}
+
+base::MemoryMappedFile::Region GlobalDescriptors::GetRegion(Key key) const {
+  for (const auto& i : descriptors_) {
+    if (i.key == key)
+      return i.region;
+  }
+  DLOG(FATAL) << "Unknown global descriptor: " << key;
+  return base::MemoryMappedFile::Region::kWholeFile;
 }
 
 void GlobalDescriptors::Reset(const Mapping& mapping) {
diff --git a/base/posix/global_descriptors.h b/base/posix/global_descriptors.h
index 3d7369c31..c774634 100644
--- a/base/posix/global_descriptors.h
+++ b/base/posix/global_descriptors.h
@@ -12,6 +12,7 @@
 
 #include <stdint.h>
 
+#include "base/files/memory_mapped_file.h"
 #include "base/memory/singleton.h"
 
 namespace base {
@@ -36,8 +37,18 @@ namespace base {
 class BASE_EXPORT GlobalDescriptors {
  public:
   typedef uint32_t Key;
-  typedef std::pair<Key, int> KeyFDPair;
-  typedef std::vector<KeyFDPair> Mapping;
+  struct Descriptor {
+    Descriptor(Key key, int fd);
+    Descriptor(Key key, int fd, base::MemoryMappedFile::Region region);
+
+    // Globally unique key.
+    Key key;
+    // Actual FD.
+    int fd;
+    // Optional region, defaults to kWholeFile.
+    base::MemoryMappedFile::Region region;
+  };
+  typedef std::vector<Descriptor> Mapping;
 
   // Often we want a canonical descriptor for a given Key. In this case, we add
   // the following constant to the key value:
@@ -53,12 +64,19 @@ class BASE_EXPORT GlobalDescriptors {
   // Get a descriptor given a key. It is a fatal error if the key is not known.
   int Get(Key key) const;
 
-  // Get a descriptor give a key. Returns -1 on error.
+  // Get a descriptor given a key. Returns -1 on error.
   int MaybeGet(Key key) const;
 
-  // Set the descriptor for the given key.
+  // Get a region given a key. It is a fatal error if the key is not known.
+  base::MemoryMappedFile::Region GetRegion(Key key) const;
+
+  // Set the descriptor for the given |key|. This sets the region associated
+  // with |key| to kWholeFile.
   void Set(Key key, int fd);
 
+  // Set the descriptor and |region| for the given |key|.
+  void Set(Key key, int fd, base::MemoryMappedFile::Region region);
+
   void Reset(const Mapping& mapping);
 
  private: