Add fallback lookup for eglGetProcAddress

Use the GLContext to find address for eglGetProcAddress symbol, if it's
not found with dlopen.
Index: qtwebengine-opensource-src-5.11.1+dfsg/src/core/gl_context_qt.cpp
===================================================================
--- qtwebengine-opensource-src-5.11.1+dfsg.orig/src/core/gl_context_qt.cpp
+++ qtwebengine-opensource-src-5.11.1+dfsg/src/core/gl_context_qt.cpp
@@ -155,6 +155,17 @@ QFunctionPointer GLContextHelper::getGlX
     return get_proc_address;
 }
 
+QFunctionPointer GLContextHelper::getEglGetProcAddress()
+{
+     QFunctionPointer get_proc_address = nullptr;
+#ifndef QT_NO_OPENGL
+    if (QOpenGLContext *context = qt_gl_global_share_context()) {
+        get_proc_address = context->getProcAddress("eglGetProcAddress");
+    }
+#endif
+    return get_proc_address;
+}
+
 QT_END_NAMESPACE
 
 #if defined(USE_OZONE) || defined(OS_WIN)
Index: qtwebengine-opensource-src-5.11.1+dfsg/src/core/gl_context_qt.h
===================================================================
--- qtwebengine-opensource-src-5.11.1+dfsg.orig/src/core/gl_context_qt.h
+++ qtwebengine-opensource-src-5.11.1+dfsg/src/core/gl_context_qt.h
@@ -63,6 +63,7 @@ public:
     static void* getXDisplay();
     static void* getNativeDisplay();
     static QFunctionPointer getGlXGetProcAddress();
+    static QFunctionPointer getEglGetProcAddress();
 private:
     Q_INVOKABLE bool initializeContextOnBrowserThread(gl::GLContext* context, gl::GLSurface* surface, gl::GLContextAttribs attribs);
 
Index: qtwebengine-opensource-src-5.11.1+dfsg/src/core/gl_surface_qt.cpp
===================================================================
--- qtwebengine-opensource-src-5.11.1+dfsg.orig/src/core/gl_surface_qt.cpp
+++ qtwebengine-opensource-src-5.11.1+dfsg/src/core/gl_surface_qt.cpp
@@ -227,6 +227,10 @@ bool InitializeStaticGLBindings(GLImplem
               base::GetFunctionPointerFromNativeLibrary(library,
                                                         "eglGetProcAddress"));
       if (!get_proc_address) {
+          QFunctionPointer address = GLContextHelper::getEglGetProcAddress();
+          get_proc_address = reinterpret_cast<gl::GLGetProcAddressProc>(address);
+      }
+      if (!get_proc_address) {
         LOG(ERROR) << "eglGetProcAddress not found.";
         base::UnloadNativeLibrary(library);
         return false;