Revert "Revert "Load app images""

This reverts commit 1bc977cf2f8199311a97f2ba9431a184540e3e9c.

Bug: 22858531

Change-Id: Ide00bf3a73a02cba3bb364177204ad1b13f70295
diff --git a/runtime/gc/space/image_space.h b/runtime/gc/space/image_space.h
index 9c8e8b2..f2f4163 100644
--- a/runtime/gc/space/image_space.h
+++ b/runtime/gc/space/image_space.h
@@ -35,7 +35,7 @@
     return kSpaceTypeImageSpace;
   }
 
-  // Create a Space from an image file for a specified instruction
+  // Create a boot image space from an image file for a specified instruction
   // set. Cannot be used for future allocation or collected.
   //
   // Create also opens the OatFile associated with the image file so
@@ -43,10 +43,16 @@
   // creation of the alloc space. The ReleaseOatFile will later be
   // used to transfer ownership of the OatFile to the ClassLinker when
   // it is initialized.
-  static ImageSpace* Create(const char* image,
-                            InstructionSet image_isa,
-                            bool secondary_image,
-                            std::string* error_msg)
+  static ImageSpace* CreateBootImage(const char* image,
+                                     InstructionSet image_isa,
+                                     bool secondary_image,
+                                     std::string* error_msg)
+      SHARED_REQUIRES(Locks::mutator_lock_);
+
+  // Try to open an existing app image space.
+  static ImageSpace* CreateFromAppImage(const char* image,
+                                        const OatFile* oat_file,
+                                        std::string* error_msg)
       SHARED_REQUIRES(Locks::mutator_lock_);
 
   // Reads the image header from the specified image location for the
@@ -144,15 +150,17 @@
   }
 
  protected:
-  // Tries to initialize an ImageSpace from the given image path,
-  // returning null on error.
+  // Tries to initialize an ImageSpace from the given image path, returning null on error.
   //
-  // If validate_oat_file is false (for /system), do not verify that
-  // image's OatFile is up-to-date relative to its DexFile
-  // inputs. Otherwise (for /data), validate the inputs and generate
-  // the OatFile in /data/dalvik-cache if necessary.
-  static ImageSpace* Init(const char* image_filename, const char* image_location,
-                          bool validate_oat_file, std::string* error_msg)
+  // If validate_oat_file is false (for /system), do not verify that image's OatFile is up-to-date
+  // relative to its DexFile inputs. Otherwise (for /data), validate the inputs and generate the
+  // OatFile in /data/dalvik-cache if necessary. If the oat_file is null, it uses the oat file from
+  // the image.
+  static ImageSpace* Init(const char* image_filename,
+                          const char* image_location,
+                          bool validate_oat_file,
+                          const OatFile* oat_file,
+                          std::string* error_msg)
       SHARED_REQUIRES(Locks::mutator_lock_);
 
   OatFile* OpenOatFile(const char* image, std::string* error_msg) const