Do not force gl-egl ANGLE backend on Linux

Let Chromium decide which ANGLE backend to use by keeping "default"
setting. The "gl" backend is available since
75b0d12 Add "default" and "gl" ANGLE implementation support to Ozone

Reportedly, the "gl-egl" backend doesn't work properly with certain GPU
drivers under X11.

Task-number: QTBUG-135786
Pick-to: 6.8 6.9
Change-Id: I1592e3c480059b0cd17831ba375ff709f00791cc
Reviewed-by: Allan Sandfeld Jensen <[email protected]>

Author: stampho

src/core/web_engine_context.cpp

@@ -882,18 +882,11 @@ WebEngineContext::WebEngineContext()
                       == gl::kGLImplementationANGLEName);
     }
 
-    if (usingANGLE && !parsedCommandLine->HasSwitch(switches::kUseANGLE)) {
-        parsedCommandLine->AppendSwitchASCII(switches::kUseANGLE,
-                                             gl::kANGLEImplementationOpenGLEGLName);
-    }
-
 #if QT_CONFIG(webengine_vulkan)
     if (QQuickWindow::graphicsApi() == QSGRendererInterface::OpenGL && usingSupportedSGBackend()) {
         if (usingANGLE && !isGbmSupported()) {
             qWarning("GBM is not supported with the current configuration. "
                      "Fallback to Vulkan rendering in Chromium.");
-            parsedCommandLine->AppendSwitchASCII(switches::kUseANGLE,
-                                                 gl::kANGLEImplementationDefaultName);
             parsedCommandLine->AppendSwitchASCII(switches::kUseVulkan,
                                                  switches::kVulkanImplementationNameNative);
             enableFeatures.push_back(features::kVulkan.name);