predictors: Refactor resource_prefetch_predictor triggering.

chrome/browser/predictors/loading_predictor.cc

Index: chrome/browser/predictors/loading_predictor.cc
diff --git a/chrome/browser/predictors/loading_predictor.cc b/chrome/browser/predictors/loading_predictor.cc
index d5bd264009427aead4df1a4926e85807fee38f60..5c6a14e4cff9bb63dcee5159196357fb1ead21fb 100644
--- a/chrome/browser/predictors/loading_predictor.cc
+++ b/chrome/browser/predictors/loading_predictor.cc
@@ -10,15 +10,15 @@
 namespace predictors {
 
 LoadingPredictor::LoadingPredictor(const LoadingPredictorConfig& config,
-                                   Profile* profile) {
-  resource_prefetch_predictor_ =
-      base::MakeUnique<ResourcePrefetchPredictor>(config, profile);
-}
+                                   Profile* profile)
+    : resource_prefetch_predictor_(
+          base::MakeUnique<ResourcePrefetchPredictor>(config, profile)) {}

[alexilin, 2017/05/23 11:01:38]

Do you think it's better to construct the pointer through the copy constructor
instead of using the constructor taking a raw pointer?

My suggestion is to use operator new:
resource_prefetch_predictor_(new ResourcePrefetchPredictor(config, profile))

[Benoit L, 2017/05/29 16:45:14]

We are trying to remove "new" as possible from Chrome, see
https://groups.google.com/a/chromium.org/forum/?utm_medium=email&utm_source=f...

In this case the generated code is highly likely to be the same.

 
 LoadingPredictor::~LoadingPredictor() = default;
 
 void LoadingPredictor::PrepareForPageLoad(const GURL& url, HintOrigin origin) {
-  resource_prefetch_predictor_->StartPrefetching(url, origin);
+  if (resource_prefetch_predictor_->CanPrefetchUrlForOrigin(url, origin))

[alexilin, 2017/05/23 11:01:38]

Shouldn't it be like LoadingPredictor tries to get a prediction for Prefetch and
calls ResourcePrefetcher directly if success?
According to our plans, ResourcePrefetchPredictor should eventually disappear
and LoadingPredictor should consult right with GlowplugDatabase.
Do you think we need to keep different types of predictors as abstractions
between LoadingPredictor and Database?

[Benoit L, 2017/05/29 16:45:14]

That's the eventual goal yes, but it doesn't seem that all is ready yet to get
there, hence it stays for now.

+    resource_prefetch_predictor_->StartPrefetching(url, origin);
 }
 
 void LoadingPredictor::CancelPageLoadHint(const GURL& url) {