chore: Replace proxy methods with utils implementation

PiperOrigin-RevId: 864802559

src/google/adk/models/apigee_llm.py

@@ -25,7 +25,6 @@ from google.adk import version as adk_version
 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
 
@@ -146,7 +145,7 @@ class ApigeeLlm(Gemini):
       kwargs_for_http_options['api_version'] = self._api_version
     http_options = types.HttpOptions(
         base_url=self._proxy_url,
-        headers=merge_tracking_headers(self._custom_headers),
+        headers=self._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 @@ class Gemini(BaseLlm):
     if llm_request.config:
       if not llm_request.config.http_options:
         llm_request.config.http_options = types.HttpOptions()
-      llm_request.config.http_options.headers = merge_tracking_headers(
+      llm_request.config.http_options.headers = self._merge_tracking_headers(
           llm_request.config.http_options.headers
       )
 
@@ -303,7 +303,7 @@ class Gemini(BaseLlm):
 
     return Client(
         http_options=types.HttpOptions(
-            headers=get_tracking_headers(),
+            headers=self._tracking_headers(),
             retry_options=self.retry_options,
         )
     )
@@ -316,6 +316,9 @@ class Gemini(BaseLlm):
         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:
@@ -331,7 +334,7 @@ class Gemini(BaseLlm):
 
     return Client(
         http_options=types.HttpOptions(
-            headers=get_tracking_headers(), api_version=self._live_api_version
+            headers=self._tracking_headers(), api_version=self._live_api_version
         )
     )
 
@@ -355,7 +358,7 @@ class Gemini(BaseLlm):
       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 = (
-          merge_tracking_headers(
+          self._merge_tracking_headers(
               llm_request.live_connect_config.http_options.headers
           )
       )
@@ -448,6 +451,10 @@ class Gemini(BaseLlm):
           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,