Simplify ExtensionInstallChecker into a single-use class

chrome/browser/extensions/crx_installer.h

Index: chrome/browser/extensions/crx_installer.h
diff --git a/chrome/browser/extensions/crx_installer.h b/chrome/browser/extensions/crx_installer.h
index 7d7168faefe45e2403f4c5cce3abac9cdadadd6f..524a9fd230529190332fd43704bd604503be2da9 100644
--- a/chrome/browser/extensions/crx_installer.h
+++ b/chrome/browser/extensions/crx_installer.h
@@ -5,6 +5,7 @@
 #ifndef CHROME_BROWSER_EXTENSIONS_CRX_INSTALLER_H_
 #define CHROME_BROWSER_EXTENSIONS_CRX_INSTALLER_H_
 
+#include <memory>
 #include <string>
 #include <vector>
 
@@ -200,9 +201,9 @@ class CrxInstaller : public SandboxedUnpackerClient {
 
   bool did_handle_successfully() const { return did_handle_successfully_; }
 
-  Profile* profile() { return install_checker_.profile(); }
+  Profile* profile() { return profile_; }
 
-  const Extension* extension() { return install_checker_.extension().get(); }
+  const Extension* extension() { return extension_.get(); }
 
   // The currently installed version of the extension, for updates. Will be
   // invalid if this isn't an update.
@@ -288,6 +289,12 @@ class CrxInstaller : public SandboxedUnpackerClient {
       install_flags_ &= ~flag;
   }
 
+  // The Profile the extension is being installed in.
+  Profile* profile_;
+
+  // The extension being installed.
+  scoped_refptr<const Extension> extension_;
+
   // The file we're installing.
   base::FilePath source_file_;
 
@@ -438,7 +445,7 @@ class CrxInstaller : public SandboxedUnpackerClient {
   int install_flags_;
 
   // Performs requirements, policy and blacklist checks on the extension.
-  ExtensionInstallChecker install_checker_;
+  std::unique_ptr<ExtensionInstallChecker> install_checker_;

[Devlin, 2017/03/16 19:29:40]

optional: Truthfully, given the (lack of) complexity of ExtensionInstallChecker
to initialize, it's probably just as cheaper or cheaper overall to avoid the
heap allocation this requires.  But... this isn't performance sensitive code. 
So whichever you prefer.

If you opt for this route, you can remove the include and replace it with a
forward declaration.

[michaelpg, 2017/03/17 04:25:22]

I checked when I was considering using base::Optional (to avoid the heap
allocation). As a member, it'd add about 100 bytes to the class size. Not a ton,
but not trivial.

I like the pointer (or Optional) for the semantics of "this doesn't always
exist".
Done.

 
   DISALLOW_COPY_AND_ASSIGN(CrxInstaller);
 };