Add UMA histograms to AsyncResourceHandler to track content size.

content/browser/loader/async_resource_handler.cc

Index: content/browser/loader/async_resource_handler.cc
diff --git a/content/browser/loader/async_resource_handler.cc b/content/browser/loader/async_resource_handler.cc
index d55bc0f9a72c14c08eeacd3c26729415dee696b6..2eaa22bdb7de434b6582b0e7615aa968291440ad 100644
--- a/content/browser/loader/async_resource_handler.cc
+++ b/content/browser/loader/async_resource_handler.cc
@@ -72,6 +72,15 @@ void InitializeResourceBufferConstants() {
   GetNumericArg("resource-buffer-max-allocation-size", &kMaxAllocationSize);
 }
 
+enum ExpectedContentSize {
+  EQ_RESPONSE_BODY = 0,
+  EQ_RESPONSE_BODY_MT_EQ_BUFFER_SIZE = 1,
+  LT_RESPONSE_BODY = 2,
+  MT_RESPONSE_BODY = 3,
+  UNKNOWN = 4,
+  EXPECTED_CONTENT_MAX,
+};
+
 }  // namespace
 
 // Used when kOptimizeLoadingIPCForSmallResources is enabled.
@@ -191,14 +200,14 @@ class DependentIOBuffer : public net::WrappedIOBuffer {
   scoped_refptr<ResourceBuffer> backing_;
 };
 
-AsyncResourceHandler::AsyncResourceHandler(
-    net::URLRequest* request,
-    ResourceDispatcherHostImpl* rdh)
+AsyncResourceHandler::AsyncResourceHandler(net::URLRequest* request,
+                                           ResourceDispatcherHostImpl* rdh)
     : ResourceHandler(request),
       ResourceMessageDelegate(request),
       rdh_(rdh),
       pending_data_count_(0),
       allocation_size_(0),
+      total_read_body_bytes_(0),
       did_defer_(false),
       has_checked_for_sufficient_resources_(false),
       sent_received_response_msg_(false),
@@ -395,6 +404,8 @@ bool AsyncResourceHandler::OnReadCompleted(int bytes_read, bool* defer) {
 
   buffer_->ShrinkLastAllocation(bytes_read);
 
+  total_read_body_bytes_ += bytes_read;
+
   if (!sent_data_buffer_msg_) {
     base::SharedMemoryHandle handle = base::SharedMemory::DuplicateHandle(
         buffer_->GetSharedMemory().handle());
@@ -551,6 +562,40 @@ void AsyncResourceHandler::RecordHistogram() {
   }
 
   inlining_helper_->RecordHistogram(elapsed_time);
+
+  // Record if content size was known in advance.
+  int64_t expected_content_size = request()->GetExpectedContentSize();
+  if (expected_content_size >= 0) {

[mmenke, 2017/01/13 16:01:36]

Having ExpectedContentSize be an enum that's not a size is a bit confusing,
particularly when we have a local variable expected_content_size that is a size.

Maybe rename ExpectedContentSize to ExpectedContentSizeResult or
ExpectedContentSizeCategory or somesuch.

[maksims (do not use this acc), 2017/01/16 07:25:22]

Done.

+    // Compare response body size to expected content size.
+    if (expected_content_size == total_read_body_bytes_ &&
+        expected_content_size >= kBufferSize) {
+      UMA_HISTOGRAM_ENUMERATION(
+          "Net.ResourceLoader.ExpectedContentSize.CorrespondsBodySize",

[mmenke, 2017/01/13 16:01:36]

Suggest just replacing "ExpectedContentSize.CorrespondsBodySize" with whatever
we use for the above enumeration (Now that we only have one histogram, don't
need to subdivide it further).

[maksims (do not use this acc), 2017/01/16 07:25:22]

Done.

+          ExpectedContentSize::EQ_RESPONSE_BODY_MT_EQ_BUFFER_SIZE,
+          ExpectedContentSize::EXPECTED_CONTENT_MAX);

[mmenke, 2017/01/13 16:01:36]

You only need one UMA_HISTOGRAM_ENUMERATION call here.

ExpectedContentSize expected_size = ExpectedContentSize::UNKNOWN;
if (expected_content_size >= 0) {
  if (...) {
    expected_size = ...;
  } else {
    ...
  }
}
UMA_HISTOGRAM_ENUMERATION(...);

[maksims (do not use this acc), 2017/01/16 07:25:21]

Done.

+    } else if (expected_content_size == total_read_body_bytes_) {
+      UMA_HISTOGRAM_ENUMERATION(
+          "Net.ResourceLoader.ExpectedContentSize.CorrespondsBodySize",
+          ExpectedContentSize::EQ_RESPONSE_BODY,
+          ExpectedContentSize::EXPECTED_CONTENT_MAX);
+    } else if (expected_content_size < total_read_body_bytes_) {
+      UMA_HISTOGRAM_ENUMERATION(
+          "Net.ResourceLoader.ExpectedContentSize.CorrespondsBodySize",
+          ExpectedContentSize::LT_RESPONSE_BODY,
+          ExpectedContentSize::EXPECTED_CONTENT_MAX);
+    } else {
+      UMA_HISTOGRAM_ENUMERATION(
+          "Net.ResourceLoader.ExpectedContentSize.CorrespondsBodySize",
+          ExpectedContentSize::MT_RESPONSE_BODY,
+          ExpectedContentSize::EXPECTED_CONTENT_MAX);
+    }
+  } else {
+    UMA_HISTOGRAM_ENUMERATION(
+        "Net.ResourceLoader.ExpectedContentSize.CorrespondsBodySize",
+        ExpectedContentSize::UNKNOWN,
+        ExpectedContentSize::EXPECTED_CONTENT_MAX);
+  }
+  total_read_body_bytes_ = 0;

[mmenke, 2017/01/13 16:01:36]

Not needed.  This class is only used to read one response body before
destruction, to don't need to clear this.

[maksims (do not use this acc), 2017/01/16 07:25:21]

Done.

 }
 
 void AsyncResourceHandler::SendUploadProgress(int64_t current_position,