DevTools: Accessibility.enable and disable protocol methods

This will allow for new methods that operate on AXNodeIds, like
Accessibility.click and Accessibility.focus. It also allows multiple
calls to getFullAXTree to be compared.

Bug: 887173
Change-Id: Iaaf103bced9c5dbc9dd04306c2562044f50dfd2c
Reviewed-on: https://chromium-review.googlesource.com/c/1237526
Commit-Queue: Joel Einbinder <einbinder@chromium.org>
Reviewed-by: Dmitry Gozman <dgozman@chromium.org>
Cr-Commit-Position: refs/heads/master@{#599847}

third_party/WebKit/LayoutTests/http/tests/devtools/agents-enable-disable-expected.txt

 Test that each agent could be enabled/disabled separately.
 
+Accessibility.disable finished successfully
 Animation.disable finished successfully
 CSS.disable finished successfully
 DOM.disable finished successfully
@@ -18,6 +19,9 @@ Performance.disable finished successfully
 Profiler.disable finished successfully
 Runtime.disable finished successfully
 
+Accessibility.enable finished successfully
+Accessibility.disable finished successfully
+
 Animation.enable finished successfully
 Animation.disable finished successfully
 

third_party/blink/renderer/core/inspector/browser_protocol.pdl

@@ -178,6 +178,13 @@ experimental domain Accessibility
       # The backend ID for the associated DOM node, if any.
       optional DOM.BackendNodeId backendDOMNodeId
 
+  # Disables the accessibility domain.
+  command disable
+
+  # Enables the accessibility domain which causes `AXNodeId`s to remain consistent between method calls.
+  # This turns on accessibility for the page, which can impact performance until accessibility is disabled.
+  command enable
+
   # Fetches the accessibility node and partial accessibility tree for this DOM node, if it exists.
   experimental command getPartialAXTree
     parameters

third_party/blink/renderer/modules/accessibility/inspector_accessibility_agent.cc

@@ -5,7 +5,6 @@
 #include "third_party/blink/renderer/modules/accessibility/inspector_accessibility_agent.h"
 
 #include <memory>
-#include "third_party/blink/renderer/core/accessibility/ax_context.h"
 #include "third_party/blink/renderer/core/accessibility/ax_object_cache.h"
 #include "third_party/blink/renderer/core/dom/dom_node_ids.h"
 #include "third_party/blink/renderer/core/dom/element.h"
@@ -499,10 +498,22 @@ std::unique_ptr<AXValue> CreateRoleNameValue(ax::mojom::Role role) {
 
 }  // namespace
 
+using EnabledAgentsMultimap =
+    HeapHashMap<WeakMember<LocalFrame>,
+                HeapHashSet<Member<InspectorAccessibilityAgent>>>;
+
+EnabledAgentsMultimap& EnabledAgents() {
+  DEFINE_STATIC_LOCAL(Persistent<EnabledAgentsMultimap>, enabled_agents,
+                      (new EnabledAgentsMultimap()));
+  return *enabled_agents;
+}
+
 InspectorAccessibilityAgent::InspectorAccessibilityAgent(
     InspectedFrames* inspected_frames,
     InspectorDOMAgent* dom_agent)
-    : inspected_frames_(inspected_frames), dom_agent_(dom_agent) {}
+    : inspected_frames_(inspected_frames),
+      dom_agent_(dom_agent),
+      enabled_(&agent_state_, /*default_value=*/false) {}
 
 Response InspectorAccessibilityAgent::getPartialAXTree(
     Maybe<int> dom_node_id,
@@ -830,6 +841,55 @@ void InspectorAccessibilityAgent::AddChildren(
   }
 }
 
+void InspectorAccessibilityAgent::EnableAndReset() {
+  enabled_.Set(true);
+  LocalFrame* frame = inspected_frames_->Root();
+  if (!EnabledAgents().Contains(frame)) {
+    EnabledAgents().Set(frame,
+                        HeapHashSet<Member<InspectorAccessibilityAgent>>());
+  }
+  EnabledAgents().find(frame)->value.insert(this);
+  CreateAXContext();
+}
+
+protocol::Response InspectorAccessibilityAgent::enable() {
+  if (!enabled_.Get())
+    EnableAndReset();
+  return Response::OK();
+}
+
+protocol::Response InspectorAccessibilityAgent::disable() {
+  if (!enabled_.Get())
+    return Response::OK();
+  enabled_.Set(false);
+  context_ = nullptr;
+  LocalFrame* frame = inspected_frames_->Root();
+  DCHECK(EnabledAgents().Contains(frame));
+  auto it = EnabledAgents().find(frame);
+  it->value.erase(this);
+  if (it->value.IsEmpty())
+    EnabledAgents().erase(frame);
+  return Response::OK();
+}
+
+void InspectorAccessibilityAgent::Restore() {
+  if (enabled_.Get())
+    EnableAndReset();
+}
+
+void InspectorAccessibilityAgent::ProvideTo(LocalFrame* frame) {
+  if (!EnabledAgents().Contains(frame))
+    return;
+  for (InspectorAccessibilityAgent* agent : EnabledAgents().find(frame)->value)
+    agent->CreateAXContext();
+}
+
+void InspectorAccessibilityAgent::CreateAXContext() {
+  Document* document = inspected_frames_->Root()->GetDocument();
+  if (document)
+    context_ = std::make_unique<AXContext>(*document);
+}
+
 void InspectorAccessibilityAgent::Trace(blink::Visitor* visitor) {
   visitor->Trace(inspected_frames_);
   visitor->Trace(dom_agent_);

third_party/blink/renderer/modules/accessibility/inspector_accessibility_agent.h

@@ -6,6 +6,7 @@
 #define THIRD_PARTY_BLINK_RENDERER_MODULES_ACCESSIBILITY_INSPECTOR_ACCESSIBILITY_AGENT_H_
 
 #include "base/macros.h"
+#include "third_party/blink/renderer/core/accessibility/ax_context.h"
 #include "third_party/blink/renderer/core/inspector/inspector_base_agent.h"
 #include "third_party/blink/renderer/core/inspector/protocol/Accessibility.h"
 #include "third_party/blink/renderer/modules/modules_export.h"
@@ -16,6 +17,7 @@ class AXObject;
 class AXObjectCacheImpl;
 class InspectorDOMAgent;
 class InspectedFrames;
+class LocalFrame;
 
 using protocol::Accessibility::AXNode;
 using protocol::Accessibility::AXNodeId;
@@ -25,10 +27,16 @@ class MODULES_EXPORT InspectorAccessibilityAgent
  public:
   InspectorAccessibilityAgent(InspectedFrames*, InspectorDOMAgent*);
 
+  static void ProvideTo(LocalFrame* frame);
+  void CreateAXContext();
+
   // Base agent methods.
   void Trace(blink::Visitor*) override;
+  void Restore() override;
 
   // Protocol methods.
+  protocol::Response enable() override;
+  protocol::Response disable() override;
   protocol::Response getPartialAXTree(
       protocol::Maybe<int> dom_node_id,
       protocol::Maybe<int> backend_node_id,
@@ -41,6 +49,9 @@ class MODULES_EXPORT InspectorAccessibilityAgent
       override;
 
  private:
+  // Unconditionally enables the agent, even if |enabled_.Get()==true|.
+  // For idempotence, call enable().
+  void EnableAndReset();
   std::unique_ptr<AXNode> BuildObjectForIgnoredNode(
       Node* dom_node,
       AXObject*,
@@ -91,6 +102,8 @@ class MODULES_EXPORT InspectorAccessibilityAgent
 
   Member<InspectedFrames> inspected_frames_;
   Member<InspectorDOMAgent> dom_agent_;
+  InspectorAgentState::Boolean enabled_;
+  std::unique_ptr<AXContext> context_;
 
   DISALLOW_COPY_AND_ASSIGN(InspectorAccessibilityAgent);
 };

third_party/blink/renderer/modules/modules_initializer.cc

@@ -87,6 +87,7 @@
 #if defined(SUPPORT_WEBGL2_COMPUTE_CONTEXT)
 #include "third_party/blink/renderer/modules/webgl/webgl2_compute_rendering_context.h"
 #endif
+#include "third_party/blink/renderer/modules/accessibility/inspector_accessibility_agent.h"
 #include "third_party/blink/renderer/modules/webgl/webgl2_rendering_context.h"
 #include "third_party/blink/renderer/modules/webgl/webgl_rendering_context.h"
 #include "third_party/blink/renderer/modules/xr/xr_presentation_context.h"
@@ -190,6 +191,7 @@ void ModulesInitializer::InstallSupplements(LocalFrame& frame) const {
   }
   InstalledAppController::ProvideTo(frame, client->GetRelatedAppsFetcher());
   ::blink::ProvideSpeechRecognitionTo(frame);
+  InspectorAccessibilityAgent::ProvideTo(&frame);
 }
 
 void ModulesInitializer::ProvideLocalFileSystemToWorker(