Fix the crash problem of WebGL2 Query api.

third_party/WebKit/Source/modules/webgl/WebGL2RenderingContextBase.cpp

Index: third_party/WebKit/Source/modules/webgl/WebGL2RenderingContextBase.cpp
diff --git a/third_party/WebKit/Source/modules/webgl/WebGL2RenderingContextBase.cpp b/third_party/WebKit/Source/modules/webgl/WebGL2RenderingContextBase.cpp
index 6d68faaba2df29307afde851c4b63257969c50db..952591508afd358dfdabcb4df97c940210ac74a4 100644
--- a/third_party/WebKit/Source/modules/webgl/WebGL2RenderingContextBase.cpp
+++ b/third_party/WebKit/Source/modules/webgl/WebGL2RenderingContextBase.cpp
@@ -1593,6 +1593,9 @@ WebGLQuery* WebGL2RenderingContextBase::createQuery()
 
 void WebGL2RenderingContextBase::deleteQuery(WebGLQuery* query)
 {
+    if (isContextLost() || !query)
+        return;
+
     if (m_currentBooleanOcclusionQuery == query) {
         webContext()->endQueryEXT(m_currentBooleanOcclusionQuery->getTarget());
         m_currentBooleanOcclusionQuery = nullptr;
@@ -1617,6 +1620,11 @@ GLboolean WebGL2RenderingContextBase::isQuery(WebGLQuery* query)
 void WebGL2RenderingContextBase::beginQuery(GLenum target, WebGLQuery* query)
 {
     bool deleted;
+    if (!query) {
+        synthesizeGLError(GL_INVALID_OPERATION, "beginQuery", "query object is null");
+        return;
+    }
+
     if (!checkObjectToBeBound("beginQuery", query, deleted))
         return;
     if (deleted) {