Fix WebVR does not properly stop presenting if requestPresent rejects.

third_party/WebKit/Source/modules/vr/VRDisplay.cpp

Index: third_party/WebKit/Source/modules/vr/VRDisplay.cpp
diff --git a/third_party/WebKit/Source/modules/vr/VRDisplay.cpp b/third_party/WebKit/Source/modules/vr/VRDisplay.cpp
index 0c6bc0ed5a89f78159ed2d4a30dfb87394962ac2..fd470f8926c4f414ce54352103eb2c3e4772cde3 100644
--- a/third_party/WebKit/Source/modules/vr/VRDisplay.cpp
+++ b/third_party/WebKit/Source/modules/vr/VRDisplay.cpp
@@ -251,7 +251,13 @@ ScriptPromise VRDisplay::requestPresent(ScriptState* scriptState,
 
   // A valid number of layers must be provided in order to present.
   if (layers.size() == 0 || layers.size() > m_capabilities->maxLayers()) {
-    forceExitPresent();
+    if (m_isPresenting) {

[mthiesse, 2017/02/13 15:33:34]

You should fix VRDisplay::forceExitPresent(), rather than fixing all of the
callsites.

[shaobo.yan, 2017/02/14 06:12:35]

Done.

+      if (m_display) {
+        m_display->ExitPresent();
+      } else {
+        forceExitPresent();
+      }
+    }
     DOMException* exception =
         DOMException::create(InvalidStateError, "Invalid number of layers.");
     resolver->reject(exception);
@@ -262,7 +268,13 @@ ScriptPromise VRDisplay::requestPresent(ScriptState* scriptState,
   // If what we were given has an invalid source, need to exit fullscreen with
   // previous, valid source, so delay m_layer reassignment
   if (!layers[0].source()) {
-    forceExitPresent();
+    if (m_isPresenting) {
+      if (m_display) {
+        m_display->ExitPresent();
+      } else {
+        forceExitPresent();
+      }
+    }
     DOMException* exception =
         DOMException::create(InvalidStateError, "Invalid layer source.");
     resolver->reject(exception);
@@ -275,7 +287,13 @@ ScriptPromise VRDisplay::requestPresent(ScriptState* scriptState,
       m_layer.source()->renderingContext();
 
   if (!renderingContext || !renderingContext->is3d()) {
-    forceExitPresent();
+    if (m_isPresenting) {
+      if (m_display) {
+        m_display->ExitPresent();
+      } else {
+        forceExitPresent();
+      }
+    }
     DOMException* exception = DOMException::create(
         InvalidStateError, "Layer source must have a WebGLRenderingContext");
     resolver->reject(exception);
@@ -291,7 +309,13 @@ ScriptPromise VRDisplay::requestPresent(ScriptState* scriptState,
   if ((m_layer.leftBounds().size() != 0 && m_layer.leftBounds().size() != 4) ||
       (m_layer.rightBounds().size() != 0 &&
        m_layer.rightBounds().size() != 4)) {
-    forceExitPresent();
+    if (m_isPresenting) {
+      if (m_display) {
+        m_display->ExitPresent();
+      } else {
+        forceExitPresent();
+      }
+    }
     DOMException* exception = DOMException::create(
         InvalidStateError,
         "Layer bounds must either be an empty array or have 4 values");