DevTools: mark protocol methods used in Puppeteer public (non-experimental).

Change-Id: I9d00ab87636cef3227cf04d7aa05b01b809103e6
TBR: headless test
Reviewed-on: https://chromium-review.googlesource.com/744729Reviewed-by: Andrey Kosyakov <caseq@chromium.org>
Cr-Commit-Position: refs/heads/master@{#513316}

headless/lib/headless_devtools_client_browsertest.cc

@@ -1333,8 +1333,8 @@ class DomTreeExtractionBrowserTest : public HeadlessAsyncDevTooledBrowserTest,
         if (layout_node->HasInlineTextNodes()) {
           std::unique_ptr<base::ListValue> inline_text_nodes(
               new base::ListValue());
-          for (const std::unique_ptr<css::InlineTextBox>& inline_text_box :
-               *layout_node->GetInlineTextNodes()) {
+          for (const std::unique_ptr<dom_snapshot::InlineTextBox>&
+                   inline_text_box : *layout_node->GetInlineTextNodes()) {
             size_t index = inline_text_nodes->GetSize();
             inline_text_nodes->Set(index, inline_text_box->Serialize());
           }

third_party/WebKit/Source/core/inspector/InspectorDOMSnapshotAgent.cpp

@@ -323,9 +323,9 @@ int InspectorDOMSnapshotAgent::VisitLayoutTreeNode(Node* node, int node_index) {
     LayoutText* layout_text = ToLayoutText(layout_object);
     layout_tree_node->setLayoutText(layout_text->GetText());
     if (layout_text->HasTextBoxes()) {
-      std::unique_ptr<protocol::Array<protocol::CSS::InlineTextBox>>
+      std::unique_ptr<protocol::Array<protocol::DOMSnapshot::InlineTextBox>>
           inline_text_nodes =
-              protocol::Array<protocol::CSS::InlineTextBox>::create();
+              protocol::Array<protocol::DOMSnapshot::InlineTextBox>::create();
       for (const InlineTextBox* text_box = layout_text->FirstTextBox();
            text_box; text_box = text_box->NextTextBox()) {
         FloatRect local_coords_text_box_rect(text_box->FrameRect());
@@ -333,7 +333,7 @@ int InspectorDOMSnapshotAgent::VisitLayoutTreeNode(Node* node, int node_index) {
             layout_object->LocalToAbsoluteQuad(local_coords_text_box_rect)
                 .BoundingBox();
         inline_text_nodes->addItem(
-            protocol::CSS::InlineTextBox::create()
+            protocol::DOMSnapshot::InlineTextBox::create()
                 .setStartCharacterIndex(text_box->Start())
                 .setNumCharacters(text_box->Len())
                 .setBoundingBox(