chore: Replace proxy methods with utils implementation

PiperOrigin-RevId: 864773118

Author: google-genai-bot

src/google/adk/models/apigee_llm.py

@@ -25,6 +25,7 @@
 from google.genai import types
 from typing_extensions import override
 
+from ..utils._google_client_headers import merge_tracking_headers
 from ..utils.env_utils import is_env_enabled
 from .google_llm import Gemini
 
@@ -145,7 +146,7 @@ def api_client(self) -> Client:
       kwargs_for_http_options['api_version'] = self._api_version
     http_options = types.HttpOptions(
         base_url=self._proxy_url,
-        headers=self._merge_tracking_headers(self._custom_headers),
+        headers=merge_tracking_headers(self._custom_headers),
         retry_options=self.retry_options,
         **kwargs_for_http_options,
     )

src/google/adk/models/google_llm.py

@@ -192,7 +192,7 @@ async def generate_content_async(
     if llm_request.config:
       if not llm_request.config.http_options:
         llm_request.config.http_options = types.HttpOptions()
-      llm_request.config.http_options.headers = self._merge_tracking_headers(
+      llm_request.config.http_options.headers = merge_tracking_headers(
           llm_request.config.http_options.headers
       )
 
@@ -303,7 +303,7 @@ def api_client(self) -> Client:
 
     return Client(
         http_options=types.HttpOptions(
-            headers=self._tracking_headers(),
+            headers=get_tracking_headers(),
             retry_options=self.retry_options,
         )
     )
@@ -316,9 +316,6 @@ def _api_backend(self) -> GoogleLLMVariant:
         else GoogleLLMVariant.GEMINI_API
     )
 
-  def _tracking_headers(self) -> dict[str, str]:
-    return get_tracking_headers()
-
   @cached_property
   def _live_api_version(self) -> str:
     if self._api_backend == GoogleLLMVariant.VERTEX_AI:
@@ -334,7 +331,7 @@ def _live_api_client(self) -> Client:
 
     return Client(
         http_options=types.HttpOptions(
-            headers=self._tracking_headers(), api_version=self._live_api_version
+            headers=get_tracking_headers(), api_version=self._live_api_version
         )
     )
 
@@ -358,7 +355,7 @@ async def connect(self, llm_request: LlmRequest) -> BaseLlmConnection:
       if not llm_request.live_connect_config.http_options.headers:
         llm_request.live_connect_config.http_options.headers = {}
       llm_request.live_connect_config.http_options.headers = (
-          self._merge_tracking_headers(
+          merge_tracking_headers(
               llm_request.live_connect_config.http_options.headers
           )
       )
@@ -451,10 +448,6 @@ async def _preprocess_request(self, llm_request: LlmRequest) -> None:
           llm_request.config.system_instruction = None
           await self._adapt_computer_use_tool(llm_request)
 
-  def _merge_tracking_headers(self, headers: dict[str, str]) -> dict[str, str]:
-    """Merge tracking headers to the given headers."""
-    return merge_tracking_headers(headers)
-
 
 def _build_function_declaration_log(
     func_decl: types.FunctionDeclaration,