Fix Linux CI test failures and improve cache hit speed

- automate.py: skip create_prebuilt_binaries() if output dir already
  exists so CI cache hits avoid re-copying hundreds of MB each run
- cef_linux.pxd: expose cef_runtime_style_t enum and CefWindowInfo
  runtime_style field in Cython declaration
- window_info.pyx: set CEF_RUNTIME_STYLE_ALLOY for Linux windowed
  browsers (CEF 123+ requirement, already done for Windows/popup)
- cefpython.pyx: extend Initialize() pump loop timeout from 2s to 6s
  so OnContextInitialized has time to fire on slow Ubuntu 24.04 CI
- main_test.py: add --disable-gpu/--disable-gpu-compositing for Linux,
  reducing startup time and GPU process failures under xvfb

Co-Authored-By: Claude Sonnet 4.6 <noreply@anthropic.com>

Author: linesight

src/cefpython.pyx

@@ -625,15 +625,15 @@ def Initialize(applicationSettings=None, commandLineSwitches=None, **kwargs):
     # 200 * 10ms = 2 seconds max; OnContextInitialized typically fires
     # within the first few iterations.
     if ret:
-        for _ in range(200):
+        for _ in range(600):
             with nogil:
                 CefDoMessageLoopWork()
             if g_context_initialized:
                 break
             time.sleep(0.01)
         if not g_context_initialized:
             Debug("CefInitialize() WARNING: OnContextInitialized not received"
-                  " within 2 seconds")
+                  " within 6 seconds")
 
     if sys.platform.startswith("linux"):
         # Install by default.

src/extern/cef/cef_linux.pxd

@@ -12,7 +12,13 @@ cdef extern from "include/internal/cef_linux.h":
     ctypedef unsigned long CefWindowHandle
     ctypedef unsigned long CefCursorHandle
 
+    ctypedef enum cef_runtime_style_t:
+        CEF_RUNTIME_STYLE_DEFAULT
+        CEF_RUNTIME_STYLE_CHROME
+        CEF_RUNTIME_STYLE_ALLOY
+
     cdef cppclass CefWindowInfo:
+        cef_runtime_style_t runtime_style
         void SetAsChild(CefWindowHandle parent,
                         const CefRect& windowRect)
         void SetAsWindowless(CefWindowHandle parent)

src/window_info.pyx

@@ -58,6 +58,8 @@ cdef void SetCefWindowInfo(
             cefWindowInfo.SetAsChild(
                     <CefWindowHandle>windowInfo.parentWindowHandle,
                     windowRect)
+            # CEF 123+: must request Alloy runtime for native windowed rendering.
+            cefWindowInfo.runtime_style = CEF_RUNTIME_STYLE_ALLOY
 
     # POPUP WINDOW - Windows only
     IF UNAME_SYSNAME == "Windows":

tools/automate.py

@@ -678,7 +678,9 @@ def create_prebuilt_binaries():
     version_header = os.path.join(src, "include", "cef_version.h")
     dst = get_prebuilt_name(version_header)
     dst = os.path.join(Options.build_dir, dst)
-    rmdir(dst)
+    if os.path.exists(dst):
+        print("[automate.py] Already exists: %s" % dst)
+        return
     os.makedirs(dst)
     bindir = os.path.join(dst, "bin")
     libdir = os.path.join(dst, "lib")

unittests/main_test.py

@@ -150,6 +150,10 @@ def test_main(self):
             # /dev/shm is too small in CI containers; renderer subprocess
             # fails shared-memory descriptor lookup (global descriptor 7).
             switches["disable-dev-shm-usage"] = ""
+            # GPU acceleration is not available under xvfb; disabling it
+            # reduces startup time and avoids GPU process launch failures.
+            switches["disable-gpu"] = ""
+            switches["disable-gpu-compositing"] = ""
         cef.Initialize(settings, switches=switches)
         subtest_message("cef.Initialize() ok")